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Supplementary Table 3. Risk of death from breast cancer between diagnostic periods, for each molecular subtype 5 and 15 years after diagnosis (Cox regression analysis).

Supplementary Figure 2. Subtype-specific incidence rates according to age and year of birth. Blue lines: Women born before 1929. Red lines: Women born in 1929 or later. Dotted lines (red and blue) represent incidence rates of subtyped cases. Solid lines (red and blue) represent average incidence rates from 50 imputed datasets with corresponding 95% confidence intervals (CIs).

Supplementary Figure 3. Cumulative incidence of death from breast cancer according to breast cancer subtypes. A: Women diagnosed before 1995 (Gray's test: p=0.0002). B: Women diagnosed in 1995 or later (Gray's test: p

Supplementary Table 1. Characteristics of the study population used in estimations of breast cancer incidence.

Supplementary Table 2. Incidence rates and incidence rate ratios of breast cancer according to hormone and HER2 receptor status, age at diagnosis and year of birth. Observed and imputed estimates.

Supplementary Figure legends.

Supplementary Table 5. Risk of death from breast cancer between diagnostic periods, for each breast cancer subtype 5 and 15 years after diagnosis (Cox regression analysis).

Background: Secular trends in incidence and prognosis of molecular breast cancer subtypes are poorly described. We studied long-term trends in a population of Norwegian women born 1886–1977.Methods: A total of 52,949 women were followed for breast cancer incidence, and 1,423 tumors were reclassified into molecular subtypes using IHC and in situ hybridization. We compared incidence rates among women born 1886–1928 and 1929–1977, estimated age-specific incidence rate ratios (IRR), and performed multiple imputations to account for unknown subtype. Prognosis was compared for women diagnosed before 1995 and in 1995 or later, estimating cumulative risk of death and HRs.Results: Between 50 and 69 years of age, incidence rates of Luminal A and Luminal B (HER2−) were higher among women born in 1929 or later, compared with before 1929 [IRRs 50–54 years; after imputations: 3.5; 95% confidence interval (CI), 1.8–6.9 and 2.5; 95% CI, 1.2–5.2, respectively], with no clear differences for other subtypes. Rates of death were lower in women diagnosed in 1995 or later, compared to before 1995, for Luminal A (HR 0.4; 95% CI, 0.3–0.5), Luminal B (HER2−; HR 0.5; 95% CI, 0.3–0.7), and Basal phenotype (HR 0.4; 95% CI, 0.2–0.9).Conclusions: We found a strong secular incidence increase restricted to Luminal A and Luminal B (HER2−) subtypes, combined with a markedly improved prognosis for these subtypes and for the Basal phenotype.Impact: This study documents a clear secular increase in incidence and a concomitant improved prognosis for specific molecular breast cancer subtypes. Cancer Epidemiol Biomarkers Prev; 25(12); 1625–34. ©2016 AACR.

Background: Prognostic improvement over time may differ between molecular breast cancer subtypes. Methods: Molecular subtypes of breast cancer (denoted Luminal A, Luminal B (HER2-), Luminal B (HER2+), HER2 type, and Triple negative) were determined by immunohistochemistry and in situhybridization applied to tissue microarrays (TMA) from archival diagnostic material. Analyses included 1957 incident cases diagnosed in three population studies over more than 30 years of observation. To study differences in prognosis over time, we compared 10-year risk of death for each subtype between specified diagnostic periods. Results: Luminal A was most frequent (47.9%) followed by Luminal B (HER2-) (28.2%), Luminal B (HER2+) (9.0%), Triple negative (9.2%) and the HER2 subtype (5.7%). Between 1990 and 2000, the 10-year risk of death from breast cancer decreased substantially for each subtype, compared to before 1990. After 2000, the decrease continued for Luminal A and HER2 patients, but there was no further decrease for Triple negative patients. Conclusion: The observed improvement in prognosis during the 1990s may primarily be attributed to modern oncological treatment. After 2000, the improvement for Luminal A coincides with implementation of organized mammography screening, whereas the strong improvement for HER2 patients may be due to novel targeted treatment.

Background: Frozen embryo transfer (frozen-ET) is increasingly common because of improved cryopreservation methods and elective freezing of all embryos. Frozen-ET is associated with higher risk of hypertensive disorders in pregnancy than both natural conception and fresh embryo transfer (fresh-ET), but whether this is attributable to parental factors or treatment is unknown. Methods: Using the Medical Birth Registries of Denmark (1994–2014), Norway, and Sweden (1988–2015), linked to data from national quality registries and databases on assisted reproduction, we designed a population-based cohort study with within-sibship comparison. We included 4 426 691 naturally conceived, 78 300 fresh-ET, and 18 037 frozen-ET singleton pregnancies, of which 33 209 sibships were conceived using different conception methods. Adjusted odds ratios (aOR) of hypertensive disorders in pregnancy for fresh-ET and frozen-ET versus natural conception with 95% CI were estimated using multilevel logistic regression, where random effects provided conventional population-level estimates and fixed effects gave within-sibship estimates. Main models included adjustment for birth year, maternal age, parity, and country. Results: Risk of hypertensive disorders in pregnancy was higher after frozen-ET compared to natural conception, both at population-level (7.4% versus 4.3%, aOR, 1.74 [95% CI, 1.61–1.89]) and within sibships (aOR, 2.02 [95% CI, 1.72–2.39]). For fresh-ET, risk was similar to natural conception, both at population-level (aOR, 1.02 [95% CI, 0.98–1.07]) and within sibships (aOR, 0.99 [95% CI, 0.89–1.09]). Conclusions: Frozen-ET was associated with substantially higher risk of hypertensive disorders in pregnancy, even after accounting for shared parental factors within sibships.

Background Within-sibship analyses show lower perinatal mortality after assisted reproductive technology (ART) compared with natural conception (NC), a finding that appears biologically unlikely. We investigated whether this may be attributed to bias from selective fertility and carryover effects. Methods Using data from national registries in Denmark (1994–2014), Finland (1990–2014) and Norway and Sweden (1988–2015), we studied 5 722 826 singleton pregnancies, including 119 900 ART-conceived and 37 590 exposure-discordant sibships. Perinatal mortality at the population level and within sibships was compared using multilevel logistic regression with random and fixed intercepts, respectively. We estimated selective fertility as the proportion of primiparous women with and without perinatal loss who had a second delivery, and carryover effects through bidirectional and crosswise associations. Results Population analysis showed higher perinatal mortality among ART conception compared with NC (odds ratio 1.21, 95% CI 1.13 to 1.30), whereas within-sibship analysis showed the opposite (OR 0.36, 95% CI 0.31 to 0.43). Primiparous women with perinatal loss were more likely to give birth again (selective fertility) and to use ART in this subsequent pregnancy (carryover effects), resulting in strong selection of double-discordant sibships with death of the naturally conceived and survival of the ART-conceived sibling. After controlling for conception method and outcome in the first pregnancy, ART was not consistently associated with perinatal mortality in the second pregnancy. Conclusions Whereas population estimates may be biased by residual confounding, within-sibship estimates were biased by selective fertility and carryover effects. It remains unclear whether ART conception contributes to perinatal mortality.

To investigate whether risks of stillbirth and neonatal death differ after fresh embryo transfers (fresh-ETs) and frozen embryo transfers (frozen-ETs) compared with singletons conceived without medical assistance.A population-based cohort study.Not applicable.Data linkage between the nationwide Medical Birth Registries in Denmark (1994-2014), Norway and Sweden (1988-2015), and national quality registries and databases on assisted reproductive technology identified a total of 4,590,853 singletons, including 78,642 conceived by fresh-ET and 18,084 by frozen-ET.None MAIN OUTCOME MEASURE(S): Stillbirth (fetal death before and during delivery) and neonatal death (live born with death 0-27 days postpartum).Overall, 17,123 (0.37%) singletons were stillborn and 7,685 (0.17%) died neonatally. Compared with singletons conceived without medical assistance, the odds of stillbirth were similar after fresh-ET and frozen-ET, whereas the odds of neonatal death were high after fresh-ET (odds ratio [OR], 1.69; 95% confidence interval [CI], 1.46-1.95) and frozen-ET (OR, 1.51; 95% CI, 1.08-2.10). Preterm birth (37 gestational weeks) was more common after fresh-ET (8.0%) and frozen-ET (6.6%) compared with singletons conceived without medical assistance (5.0%), and strongly associated with neonatal mortality across all conception methods. Within gestational age categories, risk of stillbirth and neonatal death was similar for all conception methods, except that singletons from fresh-ET had a higher risk of stillbirth during gestational week 22-27 (OR, 1.85; 95% CI, 1.51-2.26).Overall, the risk of stillbirth was similar after fresh-ET and frozen-ET compared with singletons conceived without medical assistance, whereas neonatal mortality was high, possibly mediated by the high risk of preterm birth when compared with singletons conceived without medical assistance. Our results gave no clear support for choosing one treatment over the other.

There is concern that assisted reproductive technology (ART) may increase ovarian cancer risk, but previous studies are inconclusive. We compared ovarian cancer risk for women who gave birth after ART vs natural conception.Through linkage of nationwide registry data, we followed 3,303,880 initially nulliparous women in Denmark (1994-2014), Finland (1990-2014), Norway (1984-2015) and Sweden (1985-2015) from first pregnancy ≥22 weeks to ovarian cancer, emigration, death or end of follow-up (2014/2015). We estimated hazard ratios (HRs), adjusting for age, parity, maternal birth year and country, and for body mass index and smoking in subsamples.Mean age at first birth was 27.7 years. During a mean follow-up of 14.4 person-years, 2683 participants (0.08%) developed ovarian cancer; 135 after ART and 2548 after natural conception only (incidence rates 11.6 and 5.5 per 100,000 person-years, respectively). The risk was higher for women who ever gave birth after ART (HR 1.70, 95% confidence interval 1.42-2.03) compared to natural conception. Associations were stronger for conventional in vitro fertilisation than for intracytoplasmic sperm injection.Among parous women, ART-conception was associated with a higher risk of ovarian cancer than natural conception. Further studies should decipher whether this is causal or confounded by infertility or other factors.

Preterm birth affects lungs in several ways but only few studies have follow-up until adulthood. We investigated the association of the entire spectrum of gestational ages with specialist care episodes for obstructive airway disease (asthma and chronic obstructive pulmonary disease, COPD) at age 18–50 years. We used nationwide register data on 706 717 people born 1987–1998 in Finland (4.8% preterm) and 1 669 528 born 1967–1999 in Norway (5.0% preterm). Care episodes of asthma and COPD were obtained from specialised healthcare registers, available in Finland 2005–2016 and in Norway 2008–2017. We used logistic regression to estimate odds ratios (OR) for having a care episode with either disease outcome. Odds of any obstructive airway disease in adulthood were 2–3-fold for those born

BackgroundLong-term breast cancer incidence trends according to proliferation status are poorly described. We studied time-trends in breast cancer incidence, using mitotic count and Ki-67 as markers of proliferation.MethodsAmong 83,298 Norwegian women followed for breast cancer occurrence 1961–2012, 2995 incident breast cancers were diagnosed. Ki-67 was assessed using immunohistochemistry on tissue microarrays and mitoses were counted on whole sections. We compared incidence rates according to proliferation status among women born 1886–1928 and 1929–1977, estimating age-specific incidence rate ratios. We performed multiple imputations to account for unknown proliferation status. Mean values of Ki-67 and mitotic counts were calculated, according to age and birth year. We performed separate incidence analyses for HER2+and triple negative breast cancers.ResultsAmong women aged 40–69 years, incidence rates of tumours with low-proliferative activity were higher among those born in 1929 or later, compared to before 1929, according to Ki-67 and mitotic count. Incidence rates of tumours with high-proliferative activity were also higher in women born in 1929 or later compared to before 1929 according to Ki-67, but not according to mitotic count. Mean values of Ki-67 and mitotic count varied according to age and birth year. In subtype-specific analyses we found an increase of high-proliferative HER2+tumours according to Ki-67 in women born in 1929 or later, compared to before 1929.ConclusionsThere has been a temporal increase in both low- and high-proliferative breast cancers.

Background. Several studies have evaluated the effect of mammography screening on breast cancer mortality based on overall breast cancer mortality trends, with varied conclusions. The statistical power of such trend analyses is, however, not carefully studied. Methods. We estimated how the effect of screening on overall breast cancer mortality is likely to unfold. Because a screening effect is based on earlier treatment, screening can affect only new incident cases after screening introduction. To evaluate the likelihood of detecting screening effects on overall breast cancer mortality time trends, we calculated the statistical power of joinpoint regression analysis on breast cancer mortality trends around screening introduction using simulations. Results. We found that a very gradual increase in population-level screening effect is expected due to prescreening incident cases. Assuming 25% effectiveness of a biennial screening program in reducing breast cancer mortality among women 50 to 69 y of age, the expected reduction in overall breast cancer mortality was 3% after 2 y and reached a long-term effect of 18% after 20 y. In common settings, the statistical power to detect any screening effects using joinpoint regression analysis is very low (Highlights Population-level mammography screening effects on breast cancer mortality emerge gradually following screening introduction, resulting in very low statistical power of trend analysis. Researchers and policy makers evaluating mammography screening should avoid relying on population-wide breast cancer mortality trends. Expected mammography screening effects at population level are lower than those from screening trials, as many cases of breast cancer fall outside the screening age range.

Objective: To assess the risk of neurodevelopmental disorders in singletons born after the use of assisted reproductive technology (ART) compared with singletons born without the use of ART. Design: Nordic register-based study. Setting: Cross-linked data from Medical Birth Registers and National ART and Patient Registers; liveborn singletons in 1995-2014 in Denmark and Finland, 2005-2015 in Norway, and 1995-2015 in Sweden with follow-up to 2014 (Denmark and Finland) or 2015 (Norway and Sweden). Patients: A total of 5,076,444 singletons: 116,909 (2.3%) born with and 4,959,535 (97.7%) born without the use of ART (non-ART). Interventions: In vitro fertilization, intracytoplasmic sperm injection, and fresh and frozen embryo transfer. Main Outcome Measures: The primary outcomes (International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, codes) were learning and motor functioning disorders (F80-F83), autism spectrum disorder (F84), attention-deficit/hyperactivity disorder and conduct disorders (F90-F92), and tic disorders (F95). Crude hazard ratios (HRs) and adjusted hazard ratios (aHRs) with 95% confidence intervals were calculated. Results: Singletons in the ART cohort had a higher adjusted risk of learning and motor functioning disorders (HR, 1.01 [0.96-1.07]; aHR, 1.17 [1.11-1.24]) and a tendency toward a higher risk of autism spectrum disorder (HR, 1.12 [1.04-1.21]; aHR, 1.07 [0.98-1.16]) and attention-deficit/hyperactivity disorder and conduct disorders (HR, 0.82 [0.77-0.86]; aHR, 1.17 [0.99-1.12]) but not of tic disorders (HR, 1.21 [1.06-1.38]; aHR, 1.17 [0.96-1.27]). No differences in risk were found between children born after in vitro fertilization and intracytoplasmic sperm injection or after fresh and frozen embryo transfer. Conclusions: Our findings of only small differences in neurodevelopment between ART and non-ART singletons are reassuring and in line with previous studies. (C) 2022 by American Society for Reproductive Medicine.

The NOPHO ALL2008 is a population-based study using an unmodified pediatric protocol in patients 1-45 years of age with acute lymphoblastic leukemia. Patients with T-ALL were given a traditional pediatric scheme if fast responding (minimal residual disease (MRD) 0.1% day 29), or intensive block-based chemotherapy if slow responding (MRD 0.1% day 29). Both treatment arms included pediatric doses of high-dose methotrexate and asparaginase. If MRD ≥ 5% on day 29 or ≥0.1% after consolidation, patients were assigned to allogeneic hematopoietic stem cell transplantation. The 5-year overall survival of the 278 T-ALL patients was 0.75 (95% CI 0.69-0.81), being 0.82 (0.74-0.88) for patients 1.0-9.9 years, 0.76 (0.66-0.86) for those 10.0-17.9 years, and 0.65 (0.55-0.75) for the older patients. The risk of death in first remission was significantly higher in adults (12%) compared with the 1-9 years group (4%). The MRD responses in the three age groups were similar, and only a nonsignificant increase in relapse risk was found in adults. In conclusion, an unmodified pediatric protocol in patients 1-45 years is effective in all age groups. The traditional pediatric treatment schedule was safe for all patients, but the intensive block therapy led to a high toxic death rate in adults.

Study question Does the risk of neurodevelopmental disorders differ between singletons born after various assisted reproductive techniques (ART) and spontaneous conception (SC) until young adulthood? Summary answer ART children had a slightly increased rate of learning and motor functioning disorders, autism spectrum disorders (ASD), and ADHD and conduct disorders. What is known already Studies on the impact of ART on offspring have reported both increased risk and comparable incidences of neurodevelopmental disorders between ART and SC offspring. The most studied neurodevelopmental disorders with ART are autism spectrum disorders (ASD.) There is, however, no consensus on the risk of ASD for ART children. The risk for other neurodevelopmental disorders, like attention-deficit hyperactivity disorders (ADHD) or tic disorder among ART children, is also a debated issue, as studies are scarce. Study design, size, duration A Nordic register-based cohort study including all singleton live births (N = 5 076 444) after ART (n = 116 909) or SC (n = 4 959 535) between 1995 and 2014 in Denmark and Finland, 1995 and 2015 in Sweden; and 2005 and 2015 in Norway. Children with intellectual disability (ICD-10: F70-F79) are excluded. The children are followed up to young adulthood (the year 2014 in Denmark and Finland, and 2015 in Norway and Sweden). Participants/materials, setting, methods Offspring outcomes were defined as following ICD-10 diagnoses: learning and motor functioning disorders (F80-83), ASD (F84), ADHD and conduct disorders (F90-F92), and tic disorders/Tourette (F95). We calculated crude and adjusted hazard ratios (HR) for neurodevelopmental diagnoses using Cox regression. Adjustments were made for the country, maternal age at the delivery, parity, smoking, and maternal psychiatric morbidity. Main results and the role of chance The cumulative incidences of neurodevelopmental disorders in the cohort were 1.74% for F90-F92, 1.40% for F80-83, 0.66% for F84, and 0.22% for F95. In crude Cox-regression ART children had an increased likelihood during the follow-up of being diagnosed with F84 (HR 1.12 [95% CI 1.04-1.21]) and F95 (HR 1.21 [95% CI 1.06-1.38]), but not with F80-83 (HR 1.01 [95% CI 0.96-1.07]) or F90-92 (HR 0.82 [95% CI 0.77-0.86]). After adjustments the likelihood was increased for F80-83 (HR 1.20 [95% CI 1.13-1.27]), F84 (HR 1.12 [95% CI 1.03-1.24]), and F90-92 (HR 1.09 [95% CI 1.04-1.19]), but nor for F95 (HR 1.13 [95% CI 0.99-1.30]). After adjustments, intracytoplasmic sperm injection children compared with in vitro fertilization children had similar likelihood during follow-up for F80-83 (1.06 [95% CI 0.89–1.25]), for F84 (HR 0.92 [95% CI 0.76–1.11]), for F90-92 (HR 0.96 [95% CI 0.83–1.12]), and for F95 (HR 1.16 [95% CI 0.83–1.63]). After adjustments, frozen embryo transfer children compared with fresh embryo transfer children had similar likelihood during follow-up for F80-83 (HR 1.11 [95% CI 0.90–1.37]), F84 (HR 0.98 [95% CI 0.76–1.27]), F90-92 (HR 0.96 [95% CI 0.78–1.19]), and F95 (HR 0.83 [95% CI 0.51–1.35]). Limitations, reasons for caution There may be residual confounding by unknown or unmeasured confounders. We lack information on possible confounders like the reason and length of infertility, maternal substance use other than self-reported smoking status, paternal age, and parental somatic morbidity. Additional limitations are differences in registration practice and data availability between study countries. Wider implications of the findings This is the largest singleton cohort and the first multinational study on the risk for neurodevelopmental disorders among ART children. While the rate of some neurodevelopmental disorders was increased among ART children, the absolute risk was moderate. The type of ART did not associate with the incidence of neurodevelopmental disorders. Trial registration number ISRCTN11780826

STUDY QUESTION Is the growth pattern of children conceived by ART different compared to naturally conceived children. SUMMARY ANSWER Both ART and underlying parental subfertility may contribute to differences in early childhood growth between children conceived with and without the use of ART. WHAT IS KNOWN ALREADY Children conceived by ART weigh less and are shorter at the time of delivery. The extent to which differences in growth according to mode of conception persist during childhood, and the role of underlying parental subfertility, remains unclear. STUDY DESIGN, SIZE, DURATION We conducted a prospective study population-based study. We studied 81 461 children participating in the Norwegian Mother, Father and Child Cohort Study (MoBa) and 544 113 adolescents screened for military conscription. PARTICIPANTS/MATERIALS, SETTING, METHODS Conception by ART as registered in the Medical Birth Registry. We compared maternally reported length/height and weight among children in MoBa from mid-pregnancy to age 7 according to mode of conception using mixed-effects linear regression. Differences in self-reported height and weight at 17 years of age at screening for military conscription were assessed with linear regression. MAIN RESULTS AND THE ROLE OF CHANCE At birth, children conceived by ART were shorter (boys −0.3 cm; 95% CI, −0.5 to −0.1), girls −0.4 cm; 95% CI, −0.5 to −0.3) and lighter (boys −113 grams; 95% CI, −201 to −25, girls −107 grams; 95% CI, −197 to −17). After birth, children conceived by ART grew more rapidly, achieving both greater height and weight at age 3. Children conceived by ART had a greater height up to age 7, but did not have a greater height or weight by age 17. Naturally conceived children of parents taking longer time to conceive had growth patterns similar to ART children. Children born after frozen embryo transfer had larger ultrasound measures and were longer and heavier the first 2 years than those born after fresh embryo transfer. LIMITATIONS, REASONS FOR CAUTIONS Selection bias could have been introduced due to the modest participation rate in the MoBa cohort. Our reliance on self-reported measures of length/height and weight could have introduced measurement error. WIDER IMPLICATIONS OF THE FINDINGS : Our findings provide reassurance that offspring conceived by ART are not different in height, weight or BMI from naturally conceived once they reach adolescence. STUDY FUNDING/COMPETING INTEREST(S) Research Council of Norway; Medical Research Council; National Institute of Environmental Health Sciences. The authors have no competing interest. TRIAL REGISTRATION NUMBER N/A.

IMPORTANCE Adverse long-term outcomes in individuals born before full gestation are not confined to individuals born at extreme gestational ages. Little is known regarding mortality patterns among individuals born in the weeks close to ideal gestation, and the exact causes are not well understood; both of these are crucial for public health, with the potential for modification of risk.OBJECTIVE To examine the risk of all-cause and noncommunicable diseases (NCD) deaths among young adults born preterm and early term.DESIGN, SETTING, AND PARTICIPANTS This multinational population-based cohort study used nationwide birth cohorts from Norway, Sweden, Denmark, and Finland for individuals born between 1967 and 2002. Individuals identified at birth who had not died or emigrated were followed up for mortality from age 15 years to 2017. Analyses were performed from June 2019 to May 2020.EXPOSURES Categories of gestational age (ie, moderate preterm birth and earlier [23-33 weeks], late preterm [34-36 weeks], early term [37-38 weeks], full term [39-41 weeks] and post term [42-44 weeks]).MAIN OUTCOMES AND MEASURES All-cause mortality and cause-specific mortality from NCD, defined as cancer, diabetes, chronic lung disease, and cardiovascular disease (CVD).RESULTS A total of 6 263 286 individuals were followed up for mortality from age 15 years. Overall, 339 403 (5.4%) were born preterm, and 3 049 100 (48.7%) were women. Compared with full-term birth, the adjusted hazard ratios (aHRs) for all-cause mortality were 1.44 (95% CI, 1.34-1.55) for moderate preterm birth and earlier; 1.23 (95% CI, 1.18-1.29) for late preterm birth; and 1.12 (95% CI, 1.09-1.15) for early-term birth. The association between gestational age and all-cause mortality were stronger in women than in men (P for interaction = .03). Preterm birth was associated with 2-fold increased risks of death from CVD (aHR, 1.89; 95% CI, 1.45-2.47), diabetes (aHR, 1.98; 95% CI, 1.44-2.73), and chronic lung disease (aHR, 2.28; 95% CI, 1.36-3.82). The main associations were replicated across countries and could not be explained by familial or individual confounding factors.CONCLUSIONS AND RELEVANCE The findings of this study strengthen the evidence of increased risk of death from NCDs in young adults born preterm. Importantly, the increased death risk was found across gestational ages up to the ideal term date and includes the much larger group with early-term birth. Excess mortality associated with shorter gestational age was most pronounced for CVDs, chronic lung disease, and diabetes.

Background Because birth size appears to be positively associated with breast cancer risk, we have studied whether this risk may differ according to molecular breast cancer subtypes. Methods A cohort of 22,931 women born 1920–1966 were followed up for breast cancer occurrence from 1961 to 2012, and 870 were diagnosed during follow-up. Archival diagnostic material from 537 patients was available to determine molecular breast cancer subtype, specified as Luminal A, Luminal B (human epidermal growth factor receptor 2 (HER2)-), Luminal B (HER2+), HER2 type, and Triple negative (TN) breast cancer. Information on the women’s birth weight, birth length and head circumference at birth was used to estimate hazard ratios (HR) with 95% confidence intervals (CI) for each molecular subtype, applying Cox regression, and stratified by maternal height. Results Birth length (per 2 cm increments) was positively associated with Luminal A (HR = 1.2, 95% CI, 1.0–1.3), Luminal B (HER2+) (HR = 1.3, 95% CI, 1.0–1.7), and TN breast cancer (HR = 1.4, 95% CI, 1.0–1.9). No clear association was found for birth weight and head circumference. The positive associations of birth length were restricted to women whose mothers were relatively tall (above population median). Conclusion We found a positive association of birth length with risk of Luminal A, Luminal B (HER2+) and TN breast cancer that appears to be restricted to women whose mothers were relatively tall. This may support the hypothesis that breast cancer risk is influenced by determinants of longitudinal growth and that this finding deserves further scrutiny.

PurposeThe degree of cell proliferation is important for subclassification of breast cancers into prognostic and therapeutic groups. DTX3 has been identified as a driver of proliferation in luminal breast cancer. In this study, we describe DTX3 copy number in breast cancer primary tumours and corresponding axillary lymph node metastases, and studied associations with molecular subtype, proliferation and prognosis.MethodsUsing fluorescence in situ hybridization, we assessed DTX3 and chromosome 12 centromere (CEP12) copy number in 542 primary breast cancers and 117 lymph node metastases, from a well-described cohort of Norwegian breast cancer patients. Proliferation was expressed as mitotic counts and Ki67 score. Associations between DTX3 copy number and molecular subtype and proliferation were assessed using Pearson’sχ2test. We studied the effect of copy number increase on prognosis estimating cumulative incidence of breast cancer death and hazard ratios.ResultsMean DTX3 copy number ≥ 4 was found in 23 tumours (4%), and mean ≥ 5 in 9 tumours (1.7%). Copy number increase was found within all molecular subtypes except the 5 negative phenotype and the Luminal B (HER2 +) subtype. DTX3 copy number increase was not accompanied by an increase in CEP12. Point estimates showed that there were associations between DTX3 copy number increase and high proliferation and poor prognosis; however, precision depended on copy number cut-off.ConclusionsDTX3 copy number increase was present in a small proportion of breast cancer cases. There was an association between copy number increase and high tumour cell proliferation and poor prognosis.

STUDY QUESTION Are the decreasing multiple birth rates after ART associated with a simultaneous drop in the incidence of cerebral palsy (CP) in ART children over time? SUMMARY ANSWER The relative odds of CP in ART children have declined in the Nordic countries over the past two decades concurrently with declining multiple birth rates. WHAT IS KNOWN ALREADY In the Nordic countries, the rate of twin pregnancies after ART has decreased from 30% in the early 1990s to 4–13% in 2014, following the implementation of elective single embryo transfer (SET). Consequently, preterm birth rates have declined substantially in ART pregnancies. However, whether the risk of CP, a known consequence of preterm birth, has decreased correspondingly is still unknown. STUDY DESIGN, SIZE, DURATION Retrospective register-based cohort study based on data on all singletons, twins, and higher-order multiples born in Denmark (birth year 1994–2010), Finland (1990–2010), and Sweden (1990–2014), corresponding to 111 844 ART children and 4 679 351 spontaneously conceived children. PARTICIPANTS/MATERIAL, SETTING, METHODS Data were obtained from a large Nordic cohort of children born after ART and spontaneous conception initiated by the Committee of Nordic ART and Safety—CoNARTaS. The CoNARTaS cohort was established by cross-linking national register data using the unique personal identification number, allocated to every citizen in the Nordic countries. Data from the National Medical Birth Registers, where information on maternal, obstetric, and perinatal outcomes is recorded, were cross-linked to data from the National ART- and Patients Registers to obtain information on fertility treatments and CP diagnoses. Relative risks of CP for ART compared to spontaneous conception were estimated as odds ratios from multivariate logistic regression analyses across all birth years, as well as for the following birth year categories: 1990–1993, 1994–1998, 1999–2002, 2003–2006, 2007–2010, and 2011–2014. Analyses were made for all children and for singletons and twins, separately. MAIN RESULTS AND THE ROLE OF CHANCE The main outcome measure was the relative odds of CP in different time periods for ART versus spontaneously conceived children. CP was diagnosed in 661 ART children and 16 478 spontaneously conceived children born between 1990 and 2014. In 1990–1993, the relative odds of CP were substantially higher in all ART children (adjusted odds ratio (aOR) 2.76 (95% CI 2.03–3.67)) compared with all spontaneously conceived children, while in 2011–2014, it was only moderately higher (aOR 1.39 (95% CI 1.01–1.87)). In singletons, the higher relative odds of CP in ART children diminished over time from 1990 to 1993 (aOR 2.02 (95% CI 1.22–3.14)) to 2003–2006 (aOR 1.18 (95% CI 0.91–1. 49)) and was not significantly increased for birth cohorts 2007–2010 and 2011–2014. For ART twins versus spontaneously conceived twins, the relative odds of CP was not statistically significantly increased throughout the study period. LIMITATIONS, REASONS FOR CAUTION The main limitation of the study was a shorter follow-up time and younger age at first CP diagnosis for ART children compared with spontaneously conceived children. However, analyses ensuring a minimum of bias from differences in age at CP diagnosis and follow-up time confirmed the results, hence, we do not consider this to cause substantial bias. WIDER IMPLICATIONS OF THE FINDINGS A SET policy in ART treatments has the potential to reduce the increased risk of cerebral palsy in the ART population due to lower rates of multiple deliveries. At a time with high survival rates of frozen/thawed embryos, this study provides a strong argument against the continued use of multiple embryo transfer in most ART settings. Larger cohort studies including also the number of gestational sacs in early pregnancy will be preferable to show an effect of vanishing twins on the risk of CP in the ART population. STUDY FUNDING/COMPETING INTEREST(S) The study was financed by grants from NordForsk (grant number 71450), Elsass Foundation (19-3-0444), the ALF-agreement (ALFGBG 70940), and The Research Fund of Rigshospitalet, Copenhagen University Hospital. There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER ISRCTN11780826.

Background Children born after ART (Assisted reproductive technology) are known to be at increased risk for adverse outcomes, but there are little data on health of older children. The aim of this study is to examine puberty related outcomes of ART children as available in existing health care registers, using Nordic data. Methods The CoNARTaS cohort contains data on 121 746 ART children and 6 538 411 naturally conceived children born in Denmark (1994-2014), Finland (1990-2014), Norway (2002-2015) and Sweden (1985-2015). All data were obtained from national health registries, disease-specific quality registries and other nationwide databases. Puberty problems were defined by using ICD-10 codes and classified as any problems, late and early puberty and unspecified problems. Cox regression adjusted for maternal age, parity, plurality, maternal diabetes and maternal smoking were made, separately for girls and boys. Results 36 508 children had diagnoses related to puberty problems, of which 591 were ART-children including IVF (in vitro fertilization) and ICSI (intra cytoplasmic sperm injection). In total, ART children had increased risks for any pubertal problems (adjusted HR 1.60, 95% CI: 1.47-1.74), late puberty (1.57, 95% CI: 1.31-1.89) and early puberty (1.63, 95% CI: 1.46-1.82). The effect was similar for girls (1.61, 95% CI: 1.46-1.78) and boys (1.55, 95% CI: 1.33-1.81), but girls had more diagnoses related to early puberty (66.2%) and boys with late puberty (48.8%). ICSI was associated with higher risk (2.01, 95% CI 1.74-2.31) than IVF (1.46, 95% CI: 1.30-1.65), but the difference between fresh and frozen embryo transfer remained statistically insignificant. Conclusions Both girls and boys born after ART had the increased risk for pubertal problems. However, we could not adjust for all possible confounders such as infertility diagnoses or drugs used in ART. More studies are needed to confirm the findings and to find out reasons for the increased risks. Key messages Both girls and boys born after ART had the increased risk for pubertal problems. More studies are needed to confirm the findings and to find out reasons for the increased risks.

Background: The use of assisted reproductive technology is increasing worldwide and conception after assisted reproduction currently comprises 3%–6% of birth cohorts in the Nordic countries. The risk of placenta-mediated pregnancy complications is greater after assisted reproductive technology compared with spontaneously conceived pregnancies. Whether the excess risk of placenta-mediated pregnancy complications in pregnancies following assisted reproduction has changed over time, is unknown. Objectives: To investigate whether time trends in risk of pregnancy complications (hypertensive disorders in pregnancy, placental abruption and placenta previa) differ for pregnancies after assisted reproductive technology compared with spontaneously conceived pregnancies during 3 decades of assisted reproduction treatment in the Nordic countries. Study Design: In a population-based cohort study, with data from national health registries in Denmark (1994–2014), Finland (1990–2014), Norway (1988–2015) and Sweden (1988–2015), we included 6,830,578 pregnancies resulting in delivery. Among these, 146,998 (2.2%) were pregnancies after assisted reproduction (125,708 singleton pregnancies, 20,668 twin pregnancies and 622 of higher order plurality) and 6,683,132 (97.8%) pregnancies were conceived spontaneously (6,595,185 singleton pregnancies, 87,106 twin pregnancies and 1,289 of higher order plurality). We used logistic regression with post-estimation to estimate absolute risks and risk differences for each complication. We repeated analyses for singleton and twin pregnancies, separately. In subsamples with available information, we also adjusted for maternal body mass index, smoking during pregnancy, previous cesarean delivery, culture duration, and cryopreservation. Results: The risk of each placental complication was consistently greater in pregnancies following assisted reproductive technology compared with spontaneously conceived pregnancies across the study period, except for hypertensive disorders in twin pregnancies, where risks were similar. Risk of hypertensive disorders increased over time in twin pregnancies for both conception methods, but more strongly for pregnancies following assisted reproductive technology (risk difference, 1.73 percentage points per 5 years; 95% confidence interval, 1.35–2.11) than for spontaneously conceived twins (risk difference, 0.75 percentage points; 95% confidence interval, 0.61–0.89). No clear time trends were found for hypertensive disorders in singleton pregnancies. Risk of placental abruption decreased over time in all groups. Risk differences were –0.16 percentage points (95% confidence interval, –0.19 to –0.12) and –0.06 percentage points (95% confidence interval, –0.06 to –0.05) for pregnancies after assisted reproduction and spontaneously conceived pregnancies, respectively, for singletons and multiple pregnancies combined. Over time, the risk of placenta previa increased in pregnancies after assisted reproduction among both singletons (risk difference, 0.21 percentage points; 95% confidence interval, 0.14–0.27) and twins (risk difference, 0.30 percentage points; 95% confidence interval, 0.16–0.43), but remained stable in spontaneously conceived pregnancies. When adjusting for culture duration, the temporal increase in placenta previa became weaker in all groups of assisted reproductive technology pregnancies, whereas adjustment for cryopreservation moderately attenuated trends in assisted reproductive technology twin pregnancies. Conclusions: The risk of placenta-mediated pregnancy complications following assisted reproductive technology remains higher compared to spontaneously conceived pregnancies, despite declining rates of multiple pregnancies. For hypertensive disorders in pregnancy and placental abruption, pregnancies after assisted reproduction follow the same time trends as the background population, whereas for placenta previa, risk has increased over time in pregnancies after assisted reproductive technology.

STUDY QUESTION When do the differences in birth weights become apparent between singletons born after frozen embryo transfer (FET) and fresh embryo transfer (fresh ET)? SUMMARY ANSWER Mean birth weights after FET become significantly higher starting from gestational week (GW) 33 among boys and from GW 34 among girls. WHAT IS KNOWN ALREADY In recent years, there has been a steep rise in recorded FET treatments, enabling widespread use of elective single embryo transfer, thus reducing the risks associated with multiple gestations. However, singletons born after FET are heavier and there is a higher risk of large-for-gestational-age (LGA) (birth weight > 90 percentiles) compared to fresh ET. In contrast, risk of small-for-gestational-age (SGA, birth weight < 10 percentiles) is lower in singletons born after FET compared to fresh ET. The reasons, timing and consequences of these differences remain largely unclear. There is limited evidence about whether this difference in growth develops before the last trimester of pregnancy. STUDY DESIGN, SIZE, DURATION This retrospective Nordic register-based cohort study compared singletons born after FET (n = 17 500) to singletons born after fresh ET (n = 69 510) and natural conception (NC, n = 3 311 588). All live born singletons born between the years 2000 and 2015 in Denmark, Norway and Sweden at gestational age ≥22 weeks were included from the population-based Committee of Nordic ART and Safety (CoNARTaS) study population. PARTICIPANTS/MATERIALS, SETTING, METHODS Children born after FET were compared to those born after fresh ET and NC for mean birth weight and proportion of LGA and SGA for each GW at birth. Chi-square test and tests for relative proportions were used to compare categorical variables and Student’s t-test was used to compare continuous variables. Adjusted odds ratios (aORs) for LGA and SGA were calculated using logistic regressions, adjusting for year of birth, maternal age, parity, BMI, chronic hypertension, diabetes, smoking and offspring sex. MAIN RESULTS AND THE ROLE OF CHANCE Mean birth weights were significantly higher after FET compared to fresh ET starting from GW 33 (range from 75 g to 228 g by week) for boys and starting from GW 34 (range from 90 g to 236 g by week) for girls. Boys born after FET had a significantly higher proportion of LGA (11.0–15.1%) at birth between GW 36 and 42, compared to those born after fresh ET (7.1–9.4%) (range from P The proportion of SGA was significantly lower among boys born after FET (7.6–8.7%) compared to fresh ET (11.9–13.6%) between GW 36 and 42 (range from P LIMITATIONS, REASONS FOR CAUTION There may be residual confounding factors that we were not able to control for, most importantly the causes of preterm birth, which may also influence foetal growth. A further limitation is that we have no knowledge on growth patterns between implantation and GW 22. Finally, the number of children born extremely preterm or post-term was limited even in this large study population. WIDER IMPLICATIONS OF THE FINDINGS This is, to date, the largest study on birth weights among preterm and term ART singletons with a population-based design and NC control group. The results suggest that the freeze–thaw process is associated with higher birthweights and greater risk of LGA at least in the last trimester of pregnancy. This is an important aspect of the safety profile of ART. More research is needed on the long-term outcome of these children. STUDY FUNDING/COMPETING INTEREST(S) The CoNARTaS collaboration has received the following funding: the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk [71450], the Central Norway Regional Health Authorities [46045000], the Norwegian Cancer Society [182356-2016], the Nordic Federation of Obstetrics and Gynaecology [NF13041, NF15058, NF16026 and NF17043], the Interreg Öresund-Kattegat-Skagerrak European Regional Development Fund (ReproUnion project) and the Research Council of Norway’s Centre of Excellence funding scheme [262700]. None of the authors have any competing interests to declare. TRIAL REGISTRATION NUMBER ISRCTN11780826.

Purpose Androgen receptor (AR) expression is frequent in breast cancer and has been associated with good prognosis in several studies. The present study investigates AR-expression in relation to molecular subtypes, clinicopathological features and prognosis in 1297 primary tumours and 336 paired axillary lymph node metastases (LNM) from two cohorts of Norwegian patients. Methods Immunohistochemistry for AR was performed on tumours previously reclassified into molecular subtypes using immunohistochemistry and in situ hybridisation. Associations between AR-expression and clinical features were studied using Chi-square tests. Cumulative incidence of breast cancer death and Cox regression analyses were used to assess prognosis. Results AR-positivity was found in 78.0% of all cases, 84.9% of luminal and 45.1% of non-luminal tumours. The highest proportion of AR-positivity was found in Luminal B tumours, and the lowest in the Basal phenotype. Discordance in AR-status between primary tumours and lymph node metastases was observed in 21.4% of cases. A switch from AR− primary tumour to AR+ lymph node metastasis was seen in 60/72 discrepant cases. AR-expression in primary tumours was an independent and favourable prognostic marker (HR 0.70, 95% CI 0.55–0.90), particularly in the Luminal A subtype, and in grade 3 tumours. Conclusions AR is an independent predictor of good prognosis in BC, particularly in grade 3 and Luminal A tumours. Discordant AR-expression between primary tumour and LNM was observed in 21.4% of cases and most often there was a switch from AR− primary tumour to AR+ axillary LNM. This is a post-peer-review, pre-copyedit version of an article published in [Breast Cancer Research and Treatment] Locked until 14.8.2019 due to copyright restrictions. The final authenticated version is available online at: https://doi.org/10.1007/s10549-018-4904-x

STUDY QUESTION: Is the risk of imprinting disorders increased in children conceived after SUMMARY ANSWER: We found an adjusted odds ratio (AOR) of 2.84 [95% CI: 1.34–6.01] for Beckwith–Wiedemann syndrome in ART children, while the risk of Prader–Willi syndrome, Silver–Russell syndrome or Angelman syndrome was not increased in children conceived after ART. WHAT IS KNOWN ALREADY: Earlier studies, most of them small, have suggested an association between ART and imprinting disorders. STUDY DESIGN, SIZE, DURATION: This was a binational register-based cohort study. All children conceived by ART in Denmark (n = 45 393, born between 1994 and 2014) and in Finland (n = 29 244, born between 1990 and 2014) were identified. The full background populations born during the same time periods in the two countries were included as controls. Odds ratios of imprinting disorders in ART children compared with naturally conceived (NC) children were calculated. The median follow-up time was 8 years and 9 months for ART children and 11 years and 9 months for NC children. PARTICIPANTS/MATERIALS, SETTING, METHODS: From the national health registries in Denmark and Finland, we identified all children diagnosed with Prader–Willi syndrome (n = 143), Silver–Russell syndrome (n = 69), Beckwith–Wiedemann syndrome (n = 105) and Angelman syndrome (n = 72) born between 1994/1990 and 2014, respectively. MAIN RESULTS AND THE ROLE OF CHANCE: We identified a total of 388 children diagnosed with imprinting disorders; 16 of these were conceived after ART. The overall AOR for the four imprinting disorders in ART children compared with NC children was 1.35 [95% CI: 0.80–2.29], but since eight ART children were diagnosed with Beckwith–Wiedemann syndrome, the AOR for this specific imprinting disorder was 2.84 [95% CI: 1.34–6.01]. The absolute risk of Beckwith–Wiedemann syndrome in children conceived after ART was still low: 10.7 out of 100 000 newborns. The risks of Prader–Willi syndrome, Silver–Russell syndrome and Angelman syndrome were not increased in children conceived after ART. LIMITATIONS, REASONS FOR CAUTION: Imprinting disorders are rare events and our results are based on few ART children with imprinting disorders. The aetiology is complex and only partly clarified, and the clinical diagnoses are challenged by a broad phenotypic spectrum. WIDER IMPLICATIONS OF THE FINDINGS: In the existing studies, results on the risk of imprinting disorders in children conceived after ART are ambiguous. This study adds that the risk of imprinting disorders in ART children is very small and perhaps restricted to Beckwith–Wiedemann syndrome. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Nordic Trial Alliance: a pilot project jointly funded by the Nordic Council of Ministers and NordForsk (grant number: 71450), the Nordic Federation of Obstetrics and Gynecology (grant numbers: NF13041, NF15058, NF16026 and NF17043) and the Interreg Öresund-Kattegat-Skagerak European Regional Development Fund (ReproUnion project). The authors have no conflicts of interest related to this work. TRIAL REGISTRATION NUMBER: N/A

Purpose MRPS23 is recognized as a driver of proliferation in luminal breast cancer. The aims of the present study were to describe MRPS23 copy number change in breast cancer, and to assess associations between MRPS23 copy number change and molecular subtype, proliferation and prognosis, and between MRPS23 gene expression and molecular subtype and prognosis. Methods Using fluorescence in situ hybridization (FISH), we examined MRPS23 and centromere 17 copy number in 590 formalin-fixed, paraffin-embedded primary tumours and 144 corresponding lymph node metastases from a cohort of Norwegian breast cancer patients. Furthermore, we analysed MRPS23 gene expression data in 1971 primary breast cancer tumours from the METABRIC dataset. We used Pearson’s χ2 test to assess associations between MRPS23 copy number and molecular subtype and proliferation, and between MRPS23 expression and molecular subtype. We studied prognosis by estimating hazard ratios and cumulative incidence of death from breast cancer according to MRPS23 copy number and MRPS23 expression status. Results We found MRPS23 amplification (mean MRPS23 copy number ≥ 6 and/or MRPS23/chromosome 17 ratio ≥ 2) in 8% of primary tumours. Copy number increase associated with non-basal subtypes and higher tumour cell proliferation (Ki67). Higher MRPS23 expression associated with the Luminal B subtype. We found no significant association between MRPS23 amplification or MRSP23 gene expression, and prognosis. Conclusion Amplification of MRPS23 is associated with higher proliferation and non-basal subtypes in breast cancer. High MRPS23 expression is associated with the Luminal B subtype. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Study question Are obstetric and perinatal outcomes in pregnancies after fresh blastocyst transfer (BT) comparable with those born after fresh cleavage stage transfer (CT) and spontaneous conception (SC)? Summary answer Fresh BT is associated with a higher risk of placental and perinatal complications. What is known already BT optimizes the selection of top-quality embryos and increases pregnancy and live birth rates per transfer compared to CT. However, concerns have been raised as extended culture duration may increase obstetric complications and impair perinatal outcomes. Previous studies have shown a higher risk of preterm birth (PTB) among infants born after BT compared with CT. Pregnancies after BT are also prone to a higher risk of same-sex twins after single embryo transfer (SET). Study design, size, duration A retrospective register-based cohort study used data from Denmark, Norway and Sweden including three cohorts: 56 557 singletons and 16 315 twins born after fresh IVF/ICSI cycles and 2 808 323 SC singletons in Denmark (birth years 1997–2014), Norway (2010–2015) and Sweden (2002–2015). Of the fresh IVF/ICSI singletons, 4601 were born after BT and 51 956 after CT. The twin cohort consisted of 884 fresh IVF/ICSI children born after BT and 15 431 fresh IVF/ICSI children born after CT. Participants/materials, setting, methods Data were obtained from a large Nordic cohort of children born after ART and SC initiated by the Committee of Nordic ART and Safety (CoNARTaS). The CoNARTaS cohort was established by cross-linking National ART-, Medical Birth-, and National Patients Registers using the unique personal identification number, allocated to every citizen in the Nordic countries. Obstetric and perinatal outcomes after BT, CT and SC were compared using logistic regression analysis. For perinatal outcomes, we calculated gestational age based on the date of oocyte pick-up (OPU) and in sensitivity analyses on data from Denmark and Norway, we also calculated gestational age based on the second-trimester ultrasonography (US) scan. Risk of pregnancies with same-sex twins after SET was used as a proxy for risk of monozygotic twins. Adjustments were made for child’s sex, birth year, parity (0 or >1), maternal age, body mass index, smoking, educational level, fertilization method (IVF/ICSI), the number of aspirated oocytes, SET and country. Information on educational level and the number of aspirated oocytes was not available for Norway. Children born after frozen embryo transfer were not included. The birth cohorts were restricted according to the year in which BT was introduced in the different countries. Main results and the role of chance A higher risk of placenta previa was found in singleton pregnancies after BT compared with CT (adjusted odds ratio [aOR] 2.11 [95% CI 1.76; 2.52]). Singletons born after BT had a higher risk of PTB (aOR 1.14 [95% CI 1.01; 1.29]) compared with CT singletons, when estimated based on OPU. Furthermore, an altered male/female ratio (aOR 1.13 [95% CI 1.06; 1.21]) with more males following BT compared with CT was seen. Risk of same-sex twins after SET was higher after single BT compared with single CT (aOR 1.94 [95% CI 1.42; 2.60]). Limitations, reasons for caution Residual confounding cannot be excluded, in particular related to duration and cause of infertility that we could not adjust for due to lack of reliable data. Wider implications of the findings Extended embryo culture to the blastocyst stage has the potential to compromise obstetric and perinatal outcomes in fresh cycles. These results are important since an increasing number of IVF/ICSI treatments are performed as BT. Study funding/competing INTEREST(S) NORDFORSK (project no: 71450). The Research Fund of Rigshospitalet, Copenhagen University Hospital. ReproUnion Collaborative study, co-financed by the European Union, Interreg V ÖKS. Grants from Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (LUA/ALF 70940), Hjalmar Svensson Research Foundation. The Research Council of Norway through its Centres of Excellence funding scheme, project number 262700. None of the authors has any conflicts of interests to declare regarding this study. Trial registration number ISRCTN11780826.

STUDY QUESTION Is transfer of vitrified blastocysts associated with higher perinatal and maternal risks compared with slow-frozen cleavage stage embryos and fresh blastocysts? SUMMARY ANSWER Transfer of vitrified blastocysts is associated with a higher risk of preterm birth (PTB) when compared with slow-frozen cleavage stage embryos and with a higher risk of a large baby, hypertensive disorders in pregnancy (HDPs) and postpartum hemorrhage (PPH) but a lower risk of placenta previa when compared with fresh blastocysts. WHAT IS KNOWN ALREADY Transfer of frozen-thawed embryos (FETs) plays a central role in modern fertility treatment, limiting the risk of ovarian hyperstimulation syndrome and multiple pregnancies. Following FET, several studies report a lower risk of PTB, low birth weight (LBW) and small for gestational age (SGA) yet a higher risk of fetal macrosomia and large for gestational age (LGA) compared with fresh embryos. In recent years, the introduction of new freezing techniques has increased treatment success. The slow-freeze technique combined with cleavage stage transfer has been replaced by vitrification and blastocyst transfer. Only few studies have compared perinatal and maternal outcomes after vitrification and slow-freeze and mainly in cleavage stage embryos, with most studies indicating similar outcomes in the two groups. Studies on perinatal and maternal outcomes following vitrified blastocysts are limited. STUDY DESIGN, SIZE, DURATION This registry-based cohort study includes singletons born after frozen-thawed and fresh transfers following the introduction of vitrification in Sweden and Denmark, in 2002 and 2009, respectively. The study includes 3650 children born after transfer of vitrified blastocysts, 8123 children born after transfer of slow-frozen cleavage stage embryos and 4469 children born after transfer of fresh blastocysts during 2002–2015. Perinatal and maternal outcomes in singletons born after vitrified blastocyst transfer were compared with singletons born after slow-frozen cleavage stage transfer and singletons born after fresh blastocyst transfer. Main outcomes included PTB, LBW, macrosomia, HDP and placenta previa. PARTICIPANTS/MATERIALS, SETTING, METHODS Data were obtained from the CoNARTaS (Committee of Nordic ART and Safety) group. Based on national registries in Sweden, Finland, Denmark and Norway, the CoNARTaS cohort includes all children born after ART treatment in public and private clinics 1984–2015. Outcomes were assessed with logistic multivariable regression analysis, adjusting for the country and year of birth, maternal age, body mass index, parity, smoking, parental educational level, fertilisation method (IVF/ICSI), single embryo transfer, number of gestational sacs and the child’s sex. MAIN RESULTS AND THE ROLE OF CHANCE A higher risk of PTB ( When comparing vitrified and fresh blastocysts, we found higher risks of macrosomia (≥4500 g) aOR 1.77 [1.35–2.31] and LGA aOR 1.48 [1.18–1.84]. Further, the risks of HDP aOR 1.47 [1.19–1.81] and PPH aOR 1.68 [1.39–2.03] were higher in singletons born after vitrified compared with fresh blastocyst transfer while the risks of SGA aOR 0.58 [0.44–0.78] and placenta previa aOR 0.35 [0.25–0.48] were lower. LIMITATIONS, REASONS FOR CAUTION Since vitrification was introduced simultaneously with blastocyst transfer in Sweden and Denmark, it was not possible to explore the effect of vitrification per se in this study. WIDER IMPLICATIONS OF THE FINDINGS The results from the change of strategy to vitrification of blastocysts are reassuring, indicating that the freezing technique per se has no major influence on the perinatal and maternal outcomes. The higher risk of PTB may be related to the extended embryo culture rather than vitrification. STUDY FUNDING/COMPETING INTEREST(S) The study is part of the ReproUnion Collaborative study, co-financed by the European Union, Interreg V ÖKS. The study was also financed by grants from the Swedish state under the agreement between the Swedish government and the county councils, the ALF agreement (LUA/ALF 70940), Hjalmar Svensson Research Foundation and NordForsk (project 71 450). There are no conflicts of interest to declare. TRIAL REGISTRATION NUMBER ISRCTN11780826.

References STUDY QUESTION Do children born after assisted reproductive technology (ART) have an increased risk of developing type 1 diabetes? SUMMARY ANSWER Children born after ART were found to have an increased risk of type 1 diabetes in the unadjusted analysis, while after adjustment this association was only significant in children born after frozen embryo transfer. WHAT IS KNOWN ALREADY? Some studies raise concerns as to whether fertility treatments may influence long-term morbidity in children born after ART. Elevated blood pressure and altered glucose metabolism have been found after ART in a few studies. STUDY DESIGN, SIZE, DURATION A register-based national cohort study that included all children born in Sweden between 1985 and 2015—in total, 3 138 540 children—was carried out. PARTICIPANTS/MATERIAL, SETTING, METHODS The study was population-based and all live-born singleton children born after ART (n = 47 938) or spontaneous conception (SC) (n = 3 090 602) were included. The ART cohort comprised 36 727 children born after fresh embryo transfer and 11 211 children born after frozen embryo transfer. Several national registries were used together with data from Statistics Sweden. MAIN RESULTS AND THE ROLE OF CHANCE In total, 202 children born after ART and 17 916 children born after SC developed type 1 diabetes, corresponding to 43.4 and 35.5 per 100 000 person-years at risk (hazard ratio [HR] 1.23; 95% confidence interval [CI], 1.07 to 1.42). Mean follow-up was 9.7 (SD 6.4) years for ART children and 16.3 (SD 9.2) years for SC children. After adjustment for calendar year of birth, HR for type 1 diabetes was 1.13; 95% CI, 0.98–1.30. After further adjustment for sex, maternal age, country of birth, educational level, smoking and parental diabetes, HR was 1.07; 95% CI, 0.93–1.23. In subgroup analyses, an association was found between frozen embryo transfer and type 1 diabetes (adjusted HR 1.52; 95% CI, 1.08–2.14 and 1.41; 95% CI, 1.05–1.89 for frozen versus fresh and frozen versus SC, respectively). When comparing intracytoplasmic sperm injection to in vitro fertilization, no difference was found (adjusted HR 1.08; 95% CI, 0.77–1.51). LIMITATIONS, REASONS FOR CAUTION Limitations were the missing data and residual confounding caused by unknown confounders. Furthermore, the control group consisted of all children not conceived by ART and not non-ART children from subfertile mothers. The study was also performed in only singletons and not in the total ART population. WIDER IMPLICATIONS OF THE FINDINGS Type 1 diabetes is a serious disease, affecting human life in several ways, including risk of serious complications, reduced life span and a life-long treatment. Our results are generally reassuring, showing no increase in diabetes in ART children compared to children born after SC after adjustment for relevant confounders. The observation of an association between children born after frozen embryo transfer and type 1 diabetes, although based on subgroup analyses with a limited number of children and modest in size, is however a reason for concern. STUDY FUNDING/COMPETING INTEREST(S) This study was funded by Nordforsk 71450, the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement 70940, and the Hjalmar Svensson Foundation. The authors have no competing interests. TRIAL REGISTRATION NUMBER ISRCTN 11780826.

Purpose Proliferation is a hallmark of cancer. Using a combined genomic approach, FGD5 amplification has been identified as a driver of proliferation in Luminal breast cancer. We aimed to describe FGD5 copy number change in breast cancer, and to assess a possible association with tumour proliferation and prognosis. Methods We used fluorescence in situ hybridization targeting FGD5 and chromosome 3 centromere (CEP3) on formalin-fixed, paraffin-embedded tissue from 430 primary breast cancers and 108 lymph node metastases, from a cohort of Norwegian breast cancer patients. We tested the association between FGD5 copy number status and proliferation (assessed by Ki67 levels and mitotic count) using Pearson’s Chi square test, and assessed the prognostic impact of FGD5 copy number change by estimating cumulative risks of death and hazard ratios. Results We identified FGD5 amplification (defined as FGD5/CEP3 ratio ≥2 or mean FGD5/tumour cell ≥4) in 9.5% of tumours. Mitotic count and Ki67 levels were higher in tumours with FGD5 copy number increase, compared to tumours with no copy number change. After 10 years of follow-up, cumulative risk of death from breast cancer was higher among cases with FGD5 amplification [48.1% (95% CI 33.8–64.7)], compared to non-amplified cases [27.7% (95% CI 23.4–32.6)]. Conclusions FGD5 is a new prognostic marker in breast cancer, and increased copy number is associated with higher tumour proliferation and poorer long-term prognosis. This is a post-peer-review, pre-copyedit version of an article published in [Breast Cancer Research and Treatment]. Locked until 25.1.2019 due to copyright restrictions. The final authenticated version is available online at: https://link.springer.com/article/10.1007%2Fs10549-017-4125-8

AimsTumour microvessel density (MVD) is assessed by counting vessels in the most vascularised tumour region, the vascular hot spot. Current uncertainty regarding the prognostic role of MVD in breast cancer could, in part, be explained by variations in field area size for MVD assessment. We aimed to identify the field area size that provides the most accurate prognostic information in breast carcinoma.MethodsMVD was assessed in 212 tumours. von Willebrand factor positively stained vessels were counted in 10 consecutive visual fields in vascular hotspots. The 10 visual fields in the original counting sequence (MVD-Consecutive) were sorted from highest to lowest vessel count (MVD-Decreasing), and randomly (MVD-Random). After adding counts from one visual field at a time, mean MVD was calculated for each cumulative field area. The prognostic informativeness of each field area and sorting strategy were compared.ResultsMedian MVD decreased with increasing field size for MVD-Decreasing and MVD-Consecutive. A 0.35 mm2 total field area comprising only the highest vessel counts provided the most accurate prognostic information (MVD-Decreasing, HR for breast cancer death 1.06 per 10 vessels/mm2 increase, 95% CI 1.03 to 1.10). MVD-Decreasing gave more accurate prognostic information than MVD-Consecutive and MVD-Random, with decreasing prognostic informativeness with increasing field area.ConclusionsMedian MVD and its prognostic informativeness decreased with increasing field area. Assessing MVD in a carefully selected small field area of 0.35 mm2 provides the most accurate prognostic information. This could facilitate the implementation of MVD assessment in breast cancer.