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Objective To assess whether parents who were born small for gestational age (below the 10th birthweight centile, SGA) have increased risk of severe or mild placental abruption. To assess whether a history of SGA in other family members modifies this intergenerational effect. Design Prospective population-based observational study. Setting The Medical Birth Registry of Norway. Population From 1967 to 2013, 785 333 mother–offspring pairs, 643 066 father–offspring pairs, 272 941 maternal tetrads (i.e. her offspring, sibling, and niece/nephew), and 265 505 paternal tetrads were identified. Methods Cohort study based on linked data from the Medical Birth Registry of Norway. Main outcome measures Relative risk (RR) of severe placental abruption (preterm birth, birthweight below the 10th centile, or perinatal death) and mild placental abruption (other cases) in families with SGA. Results Mothers who were born SGA had increased risk of severe placental abruption (RR 1.5; 95% confidence interval, 95% CI 1.3–1.8), but not mild abruption. The paternal effects were weaker. The combined effect of SGA in the mother and her sibling on severe abruption was twofold (RR 2.4; 95% CI 1.7–3.3) compared with birthweight centiles ≥10 for both. Similarly, the effect of adding an SGA niece/nephew was twofold (RR 2.3; 95% CI 1.3–3.9), whereas the combined effect of SGA in the mother, her sibling and her niece/nephew was fourfold (RR 3.6; 95% CI 1.9–6.8). Conclusions Women who were born SGA have an increased risk of severe placental abruption. The corresponding paternal effect was modest. A history of SGA in other family members increases the generational effect. Tweetable abstract Women born small for gestational age have excess risk of placental abruption.

Objective To assess whether the reported excess of large for gestational age (LGA) neonates in pre-eclamptic women delivering at term is attributable to maternal obesity. Design, setting and population Population-based observational study including 77 294 singleton pregnancies registered in the Medical Birth Registry of Norway between 2007 and 2010. Methods Comparison of birthweight percentiles and z-scores between women with and without pre-eclampsia. Main outcome measures Odds ratio (OR) of LGA and z-scores of birthweight in relation to pre-eclampsia. Results Pre-eclamptic women delivering at term had increased risk of having LGA neonates. Unadjusted ORs with 95% confidence interval (95% CI) of LGA above the 90th and 95th birthweight centiles were 1.4, 95% CI 1.2–1.6 and 1.6, 95% CI 1.3–1.9, respectively. The excess of LGA persisted after including gestational diabetes and diabetes types 1 and 2 in a multivariate analysis (corresponding ORs 1.3, 95% CI 1.1–1.5 and 1.4, 95% CI 1.2–1.7), but disappeared after adjusting for maternal prepregnant body mass index (ORs 1.1, 95% CI 0.9–1.2 and 1.1, 95% CI 0.9–1.3). Conclusions This study suggests accelerated fetal growth in a subset of pre-eclamptic women delivering at term. The excess of LGA neonates is attributable to maternal obesity among pre-eclamptic women delivering at term. The maternal obesity epidemic may lead to an increased prevalence of both pre-eclampsia and LGA neonates among women delivering at term.

Objective To investigate the aggregation of obstetric anal sphincter injuries (OASIS) in relatives. Design Population-based cohort study. Setting The Medical Birth Registry of Norway from 1967 to 2008. Population All singleton, vertex-presenting infants weighing 500 g or more. Through linkage by national identification numbers, 393 856 mother–daughter pairs, 264 675 mother–son pairs, 134 889 mothers whose sisters later became mothers, 132 742 fathers whose brothers later became fathers, 131 702 mothers whose brothers later became fathers and 88 557 fathers whose sisters later became mothers were provided. Methods Comparison of women with and without a history of OASIS in their relatives. Main outcome measure Relative risk of OASIS after a previous OASIS in the family. Results The risk of OASIS was increased if the woman's mother or sister had OASIS in a delivery (aRR 1.9, 95% CI 1.6–2.3; aRR 1.7, 95% CI 1.6–1.7, respectively). If OASIS occurred in one brother's partner at delivery, the risk of OASIS in the next brother's partner was modestly increased (aRR 1.2, 95% CI 1.1–1.4). If OASIS occurred in one sister at delivery, the risk of OASIS in the brother's partner was also increased a little (aRR 1.2, 95% CI 1.1–1.4). However, there was no excess occurrence in sisters whose brothers' partners had previously had OASIS (aRR 1.1, 95% CI 0.9–1.3). Conclusions There appears to be increased familial aggregation of OASIS. These risks are stronger through the maternal rather than the paternal line of transmission, suggesting a strong genetic role that shapes aggregation of OASIS within families. These observations must be cautiously interpreted because of bias from unmeasured confounding factors may have impacted the findings.

Please cite this paper as: Waldenstrom U, Gottvall K, Rasmussen S. Caesarean section in nulliparous women of advanced maternal age has been reduced in Sweden and Norway since the 1970s: a register-based study. BJOG 2012;119:1591–1596. Objective To investigate rates of caesarean delivery in Sweden and Norway from 1973 to 2008 in relation to advanced and very advanced maternal age. Design Register study. Setting Sweden and Norway. Sample All nulliparous women aged over 30 years with a singleton pregnancy, with the fetus in a cephalic presentation, and delivering at term between 1973 and 2008 were evaluated. The study population comprised 329 824 women in Sweden and 127 810 women in Norway. Methods Data from the national Medical Birth Registers were used to describe caesarean section rates in three age groups: 30–34 years (reference group); 35–39 years (advanced age group); and ≥40 years (very advanced age group). Logistic regression analyses estimated the risk in each age group over four decades, in each of the two national samples. Results Caesarean delivery decreased from 1973–1979 to 2000–2008 in the two oldest age groups in Sweden (35–39 years, OR = 0.53, 95% CI = 0.50–0.58; ≥40 years, OR = 0.36, 95% CI = 0.30–0.43) and Norway (35–39 years, OR = 0.61, 95% CI = 0.54–0.68; ≥40 years, OR = 0.45, 95% CI = 0.34–0.58), but increased in women aged 30–34 years. The caesarean delivery rate in the two oldest groups peaked in the second half of the 1970s. Regardless of time point, the caesarean delivery rate was always highest in women aged ≥40 years, followed by women aged 35–39 years and lowest in women aged 30–34 years. Conclusions Caesarean delivery in nulliparous women of advanced and very advanced age peaked by end of the 1970s in Sweden and Norway. The subsequent reduction was contemporaneous with the introduction of electronic fetal monitoring and a more consistent use of the partogram, suggesting that more effective surveillance of labour increased the chance of a vaginal birth in these high-risk women.

Please cite this paper as: Aasheim V, Waldenstrom U, Hjelmstedt A, Rasmussen S, Pettersson H, Schytt E. Associations between advanced maternal age and psychological distress in primiparous women, f ...

Please cite this paper as: Baghestan E, Irgens L, Bordahl P, Rasmussen S. Risk of recurrence and subsequent delivery after obstetric anal sphincter injuries. BJOG 2012;119:62–69. Objective To investigate the recurrence risk, the likelihood of having further deliveries and mode of delivery after third to fourth degree obstetric anal sphincter injuries (OASIS). Design Population-based cohort study. Setting The Medical Birth Registry of Norway. Population A cohort of 828 864 mothers with singleton, vertex-presenting infants, weighing 500 g or more, during the period 1967–2004. Methods Comparison of women with and without a history of OASIS with respect to the occurrence of OASIS, subsequent delivery rate and planned caesarean rate. Main outcome measures OASIS in second and third deliveries, subsequent delivery rate and mode of delivery. Results Adjusted odds ratios of the recurrence of OASIS in women with a history of OASIS in the first, and in both the first and second deliveries, were 4.2 (95% CI 3.9–4.5; 5.6%) and 10.6 (95% CI 6.2–18.1; 9.5%), respectively, relative to women without a history of OASIS. Instrumental deliveries, in particular forceps deliveries, birthweights of 3500 g or more and large maternity units were associated with a recurrence of OASIS. Instrumental delivery did not further increase the excess recurrence risk associated with high birthweight. A man who fathered a child whose delivery was complicated by OASIS was more likely to father another child whose delivery was complicated by OASIS in another woman who gave birth in the same maternity unit (adjusted OR 2.1; 95% CI 1.2–3.7; 5.6%). However, if the deliveries took place in different maternity units, the recurrence risk was not significantly increased (OR 1.3; 95% CI 0.8–2.1; 4.4%). The subsequent delivery rate was not different in women with and without previous OASIS, whereas women with a previous OASIS were more often scheduled to caesarean delivery. Conclusion Recurrence risks in second and third deliveries were high. A history of OASIS had little or no impact on the rates of subsequent deliveries. Women with previous OASIS were delivered more frequently by planned caesarean delivery.

Please cite this paper as: Kro G, Yli B, Rasmussen S, Noren H, Amer-Wahlin I, Didrik Saugstad O, Stray-Pedersen B, Rosen K. A new tool for the validation of umbilical cord acid–base data. BJOG 2010;117:1544–1552. Objective To identify the distribution of carbon dioxide tension (pCO2) relative to pH in validated umbilical cord acid–base data. Design Observational study. Setting European hospital labour wards. Population Data for 36 432 term newborns were obtained from three sources: two trials of fetal monitoring with electrocardiography (ECG; the Swedish randomised controlled trial and the European Union Fetal ECG trial) and data from Molndal Hospital. Methods From the total study population, cases with missing values or obvious typing errors were excluded. The remaining data were validated based on specified criteria. Percentiles of arterial pCO2 by pH were calculated using multilevel regression modelling. Main outcome measures Umbilical cord pH, pCO2 and base deficit. Results Acid–base values were considered invalid in one out of seven cases. Percentiles for arterial pCO2 corresponding to specified values of arterial pH were developed from the validated data of 26 690 cases. Conclusions Percentiles for arterial pCO2 for a specified arterial pH can be used as a tool to identify cases with erroneously low pCO2 values, and thus avoid an incorrect interpretation of the newborn’s acid–base status.

Objective To produce population-based, gender- and gestational-age-specific centile curves for placental weight. Design Population study. Setting Medical Birth Registry of Norway. Population All singleton live births in Norway from 1 January 1999 to 31 December 2002. Methods In a cohort of children born in Norway, placental weights and the ratio of the birthweight to the placental weight were analysed to produce percentile curves. Main outcome measures Placental weight, birthweight-to-placental weight ratio. Results Tables and figures are presented for placental percentiles curves according to gestational age and gender. Also, tables and figures are presented for the ratio of birthweight to placental weight. CONCLUSIONS To our knowledge, this is the first time that population percentile curves have been produced for placental weights and hence for the ratio of birthweight to placental weight. These percentile curves may act as a reference for other populations as well until population-specific curves can be produced.