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Objectives Single umbilical artery (SUA) is associated with congenital malformations in most organ systems, but reported findings have not been consistent. While it has been suggested that genetic and persisting environmental factors influence the development of SUA, it is not known whether there is an increased risk of recurrence in a subsequent pregnancy of the same woman. The aims of this study were to investigate the occurrence of, and risk factors for, SUA in Norway, to assess its association with congenital malformations and trisomies 13, 18 and 21 and to study the risk of recurrence of SUA in subsequent pregnancies. Methods This was a population-based study of all (n = 918 933) singleton pregnancies of > 16 weeks' gestation recorded in the Medical Birth Registry of Norway from 1999 to 2014. To identify risk factors and congenital malformations associated with SUA, generalized estimating equations and logistic regression were used to calculate odds ratios (OR) with 95% CIs. ORs were also calculated for the recurrence of SUA in subsequent pregnancy. Results The occurrence of SUA in our population was 0.46% (4241/918 933). Parity ≥ 4, smoking, maternal pregestational diabetes, epilepsy, chronic hypertension, previous Cesarean delivery and conception by assisted reproductive technology increased the odds of having SUA. There was a particularly strong association between SUA and gastrointestinal atresia or stenosis in the neonate, with ORs of 25.8 (95% CI, 17.0-39.1) and 20.3 (95% CI, 13.4-30.9) for esophageal and anorectal atresia or stenosis, respectively, followed by an OR of 5.9 (95% CI, 1.9-18.5) for renal agenesis. SUA was associated with an up to 7-8 times increased risk of congenital heart defects. There was an association with microcephaly, congenital hydrocephalus and other congenital malformations of the brain and spinal cord. Diaphragmatic hernia, limb reductions and cleft lip or palate had a weaker association with SUA, with ORs ranging from 4.8 to 2.8. The associations with trisomy 18 and 13 were equally strong (OR 14.4 (95% CI, 9.3-22.4) and OR 13.6 (95% CI, 6.7-27.8), respectively), and the risk of trisomy 21 was doubled (OR 2.1 (95% CI, 1.2-3.6)). Pregnancies with SUA, with or without an associated malformation, had a 2-fold increased risk for SUA in a subsequent pregnancy. Conclusions SUA is associated strongly with gastrointestinal atresia or stenosis, suggesting common developmental mechanisms. The increased risk of recurrence of SUA suggests that genetic and/or persisting environmental factors influence the risk. We found that SUA had equally strong associations with trisomies 13 and 18. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Introduction Isolated single umbilical artery (iSUA) refers to single umbilical artery cords with no other fetal malformations. The association of iSUA to adverse outcome of pregnancy has not been consistently reported, and whether iSUA carries increased risk of third stage of labor complications has not been studied. We aimed to investigate the risk of adverse perinatal outcome, third stage of labor complications, and associated placental and cord characteristics in pregnancies with iSUA. A further aim was to assess the risk of recurrence of iSUA and anomalous cord or placenta characteristics in Norway. Material and methods This was a population-based study of all singleton pregnancies with gestational age >16 weeks at birth using data from the Medical Birth Registry of Norway from 1999 to 2014 (n = 918 933). Odds ratios (OR) with 95% confidence intervals were calculated for adverse perinatal outcome (preterm birth, perinatal and intrauterine death, low Apgar score, transferral to neonatal intensive care ward, placental and cord characteristics [placental weight, cord length and knots, anomalous cord insertion, placental abruption and previa]), and third stage of labor complications (postpartum hemorrhage and the need for manual placental removal or curettage) in pregnancies with iSUA, and recurrence of iSUA using generalized estimating equations and logistic regression. Results Pregnancies with iSUA carried increased risk of adverse perinatal outcome (OR 5.06, 95% confidence interval [CI] 4.26-6.02) and perinatal and intrauterine death (OR 5.62, 95% CI 4.69-6.73), and a 73% and 55% increased risk of preterm birth and small-for-gestational-age neonate, respectively. The presence of iSUA also carried increased risk of a small placenta, placenta previa and abruption, anomalous cord insertion, long cord, cord knot and third stage of labor complications. Women with iSUA, long cord or anomalous cord insertion in one pregnancy carried increased risk of iSUA in the subsequent pregnancy. Conclusions The presence of ISUA was associated with a more than five times increased risk of intrauterine and perinatal death and with placental and cord complications. The high associated risk of adverse outcome justifies follow up with assessment of fetal wellbeing in the third trimester, intrapartum surveillance and preparedness for third stage of labor complications.

INTRODUCTION Trial of labor (TOLAC) is an option in most preganancies after a cesarean section The objective of the study was to compare perinatal outcome in TOLAC and non-TOLAC deliveries in a population with high TOLAC rates. MATERIAL AND METHODS This was a cohort study based on population data from the Medical Birth Registry of Norway. We included term, cephalic, single, second deliveries, 1989-2009, after a first cesarean section (n = 43 422). TOLAC, TOLAC failure, non-TOLAC deliveries, and after high-risk and low-risk pregnancies (no risk/any risk), were compared with respect to offspring mortality, 5-minute Apgar score Apgar

INTRODUCTION The human yolk sac provides the embryo with stem cells, nutrients, and gas exchange. We hypothesized that more maternal resources, reflected in body size and body composition, would condition a a larger yolk sac, ensuring resources for the growing embryo. Thus, we aimed to determine the relation between maternal size in early pregnancy and yolk sac size. MATERIAL AND METHODS This subsidiary study was embedded in the multinational World Health Organization fetal growth project that included healthy women with a body mass index of 18-30, reliable information of their regular last menstrual period and singleton pregnancies. Yolk sac diameter, crown-rump length, and maternal height, weight, body mass index, and body composition were assessed before 13 weeks of gestation, and the fetal biometry was repeated during the pregnancy. RESULTS Of 140 participants, 122 with a successful yolk sac measurement were entered in the present analysis. Maternal weight was negatively associated with the yolk sac diameter (P = 0.007) and so was maternal height (P = 0.011), fat mass (P = 0.037), and lean body mass (P = 0.018), but not body mass index (P = 0.121). Significant effects were predominantly due to the female embryos and could be traced at 24 weeks of gestation. That is, a small yolk sac : crown-rump length ratio in early pregnancy was associated with a high fetal abdominal circumference (P

Introduction Cesarean section is the single most important risk factor for postpartum infection. Where the rest of the world shows increasing trends, the cesarean section rates are low in Norway and risk factors for infection after cesarean section may differ in high and low cesarean section settings. The goal of this study was to examine independent risk factors for surgical site infection after cesarean delivery in a setting of low cesarean section rates. Material and methods We conducted a hospital-based case-control study at Haukeland University Hospital. We included women who presented to our hospital with surgical site infection after cesarean section during the years 2014–2016 (n = 75). Controls were selected at a ratio of 2:1 (n = 148). Cases and controls were compared with respect to maternal and pregnancy characteristics using uni- and multivariable logistic regression models. Main outcome measures were anticipated risk factors for surgical site infection. Results The occurrence of surgical site infection was 0.4% and 5.4% after elective and emergency cesarean section, respectively. Compared to women without surgical site infection, women with surgical site infection were almost thrice more obese before pregnancy (OR 2.8, 95% CI 1.2–7.0), four times more likely to have preexisting psychiatric conditions (OR 4.4, 95% CI 1.1–17.6), and five times more likely to receive blood transfusion (OR 5.1, 95% CI 1.4–18.8). Signs of infection during labor was a marginally significant risk factor for surgical site infection (OR 2.0, 95% CI 1.0–5.4). Conclusions Emergency cesarean section was a significant risk factor for surgical site infection. Pregestational obesity, preexisting psychiatric conditions, and blood transfusion during or following delivery, were independent risk factors for surgical site infection. Signs of infection during labor was a marginally significant risk factor. Women with either of these risk factors should be carefully monitored and evaluated for signs of infection in the postpartum period. publishedVersion

Introduction Studies on the family aggregation of postpartum hemorrhage (PPH) are scarce and with inconsistent results, and to what extent current birthweight influences recurrence between relatives remains to be studied. Further, family aggregation of PPH has been studied from an individual, but not from a public heath perspective. We aimed to investigate family aggregation of PPH in Norway, how birthweight influences these effects, and to estimate the proportion of PPH cases attributable to a family history of PPH and current birthweight. Material and methods Using data from the Medical Birth Registry of Norway, Statistics Norway, and Central Population Registry of Norway we identified individuals as newborns, parents, grandparents, and full and half-siblings, and studied 1 002 687 mother–offspring, 841 164 father–offspring, and 761 011 both-parents–offspring pairs. We used multilevel logistic regression to calculate odds ratios (OR) with 95% CI. Results If the birth of the mother but not of the father involved PPH, then the OR of PPH (>500 mL) in the next generation was 1.44 (95% CI 1.39–1.49). If the birth of the father but not of the mother involved PPH, then OR was 1.12 (95% CI 1.08–1.16). These effects were stronger in severe PPH. Recurrence between siblings was highest between full sisters (OR 1.47, 95% CI 1.41–1.52), followed by maternal half-sisters, paternal half-sisters, and partners of full brothers. A family history of PPH or birthweight of 4000 g or more accounted for ≤5% and 15% of the total number of PPH cases, respectively. Conclusions A history of PPH in relatives influenced the recurrence risk of PPH in a dose–response pattern consistent with the anticipated proportion of shared genes. The recurrence was highest through the maternal line. publishedVersion

This is the peer reviewed version of the following article: Acharya, G., Ebbing, C., Karlsen, H., Kiserud, T. & Rasmussen, S. (2019). Sex-specific reference ranges of cerebroplacental and umbilicocerebral ratios: A longitudinal study. Ultrasound in Obstetrics and Gynecology, 2019, which has been published in final form at https://doi.org/10.1002/uog.21870. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. Objectives - The ratio of middle cerebral artery (MCA) pulsatility index (PI) to umbilical artery (UA) PI, i.e. cerebro‐placental ratio (CPR), has been suggested as a measure of fetal “brain sparing” phenomenon reflecting redistribution of fetal cardiac output as a response to placental insufficiency. Observational studies have shown that low CPR values predict increased risk of adverse perinatal outcomes although evidence from randomized clinical trials is lacking. The inverse ratio, i.e. umbilico‐cerebral ratio (UCR), is preferred by some as it increases with increasing degree of fetal compromise. Monitoring fetal wellbeing requires serial assessment, and for this purpose, appropriate reference values should be based on data from longitudinal studies. However, longitudinal reference ranges for the UCR have not been established. Furthermore, the sex of the fetus influences its growth velocity, cord properties, in utero circadian rhythm, behavioral states and placental function, but whether gestational age‐dependent changes in CPR or UCR differ between male and female fetuses has not been studied. Thus, our objective was to investigate sex‐specific, gestational age‐associated serial changes in CPR and UCR during the second half of pregnancy and establish longitudinal reference ranges. Methods - This was a dual‐center prospective longitudinal study of singleton low risk pregnancies. Doppler blood flow velocity waveforms were obtained serially from the UA and MCA during 19‐41 weeks of gestation, and PIs were determined. CPR and UCR were calculated as the ratios, MCA PI/ UA PI and UA PI/ MCA PI, respectively. The course and outcome of pregnancies was recorded. Sex of the fetus was determined after delivery. Reference intervals were constructed using multilevel modelling and gestational age‐specific Z‐scores of male and female fetuses were compared. Results - Of a total of 299 pregnancies enrolled, 284 women and their fetuses (148 male and 136 female) were included in the final analysis, and 979 paired measurements of UA and MCA PIs were used to construct sex‐specific longitudinal reference intervals. Both CPR and UCR had U‐shaped curves of development during pregnancy, but with opposite directions. There was a small but significant (P=0.007) difference in z‐scores of CPR and UCR between male and female fetuses throughout the second half of pregnancy. Conclusions - We have established longitudinal reference ranges for CPR and UCR suitable for serial monitoring with possibilities to refine the assessment by fetal sex‐specific ranges and the conditioning by a previous measurement. The clinical significance of such refinements needs further evaluation.

INTRODUCTION Despite adequate glycemic control, the risks of fetal macrosomia and perinatal complications are increased in diabetic pregnancies. Adjustments of the umbilical venous distribution, including increased ductus venosus shunting, can be important fetal compensatory mechanisms, but the impact of pregestational diabetes on umbilical venous and ductus venosus flow is not known. MATERIAL AND METHODS In this prospective study, 49 women with pregestational diabetes mellitus underwent monthly ultrasound examinations from gestational week 20 to 36. The blood velocity and the mean diameters of the umbilical vein and ductus venosus were used for calculating blood flow volumes. The development of the umbilical venous flow, ductus venosus flow and ductus venosus shunt fraction (% of umbilical venous blood shunted through the ductus venosus) was compared with a reference population, and the effect of HbA1c on the ductus venosus flow was assessed. RESULTS The umbilical venous flow was larger in pregnancies with pregestational diabetes mellitus than in low-risk pregnancies (p

This is the peer reviewed version of the following article: Rossen, J., Klungsøyr, K., Albrechtsen, S., Løkkegård, E., Rasmussen, S., Bergholt, T. & Skjeldestad, F.E. (2018). Can oxytocin augmentation modify the risk of epidural analgesia by maternal age in cesarean sections? Acta Obstetricia et Gynecologica Scandinavica, 97(7), 872-879, which has been published in final form at https://doi.org/10.1111/aogs.13341. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. Introduction: Maternal age is an established risk factor for cesarean section; epidural analgesia and oxytocin augmentation may modify this association. We investigated the effects and interactions of oxytocin augmentation, epidural analgesia and maternal age on the risk of cesarean section. Material and methods: In all, 416 386 nulliparous women with spontaneous onset of labor, ≥37 weeks of gestation and singleton infants with a cephalic presentation during 2000–2011 from Norway and Denmark were included [Ten‐group classification system (Robson) group 1]. In this case‐control study the main exposure was maternal age; epidural analgesia, oxytocin augmentation, birthweight and time period were explanatory variables. Chi‐square test and logistic regression were used to estimate associations and interactions. Results: The cesarean section rate increased consistently with advancing maternal age, both overall and in strata of epidural analgesia and oxytocin augmentation. We observed strong interactions between maternal age, oxytocin augmentation and epidural analgesia for the risk of cesarean section. Women with epidural analgesia generally had a reduced adjusted odds ratio when oxytocin was used compared with when it was not used. In Norway, this applied to all maternal age groups but in Denmark only for women ≥30 years. Among women without epidural, oxytocin augmentation was associated with an increased odds ratio for cesarean section in Denmark, whereas no difference was observed in Norway. Conclusions: Oxytocin augmentation in nulliparous women with epidural analgesia is associated with a reduced risk of cesarean section in labor with spontaneous onset.

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.

Hypertensive disorders of pregnancy (HDP) tend to recur from one pregnancy to the next. The aims of the study were to assess the recurrence risk according to type of HDP defined by gestational age at birth and to examine whether recurrence is associated with the following additional risk factors for HDP: maternal age, smoking, inter delivery interval, diabetes, body mass index, as well as fetal growth restriction, and to assess temporal trends in these associations. All women with two singleton births in the Medical Birth Registry of Norway 1967-2012 (n= 742 980) were included in this population based cohort study. Logistic regression was used to calculate odds ratios for the risk of recurrent HDP according to type of HDP. The highest odds ratio of recurrence was observed for the same type of HDP based on gestational age at delivery. After gestational hypertension and term preeclampsia the risk increased tenfold for the same type to recur, whereas after late and early preterm preeclampsia, the risk increased 27 and 97 fold, respectively. The recurrence of early preterm preeclampsia was less influenced by additional risk factors than term HDP. Recurrence of early preterm HDP was significantly lower from 1993 onwards. Recurrent HDP tended to be of the same type as the previous HDP. Risk of recurrence associated with additional risk factors were observed particularly after term. The odds ratio of recurrence of early preterm HDP was significantly lower from 1993 onwards. This article is protected by copyright. All rights reserved.

Anomalous cord insertion is associated with increased risk of adverse maternal and perinatal outcome. Our aim was to study whether anomalous cord insertion is associated with prelabor rupture of membranes (PROM), preterm PROM (pPROM), long or short umbilical cord, and time trend of spontaneous preterm birth (SPTB) and anomalous cord insertion.A population-based register study using data from the Medical Birth Register of Norway including all singleton births (gestational age16 weeks and45 weeks) during 1999-2013 (n = 860 465) to calculate odds ratios (ORs) for PROM, pPROM, SPTB, and cord length (95th or5th centile) according to the cord insertion site by logistic regression with adjustment for possible confounders. We also assessed time trends of SPTB and anomalous cord insertion.Velamentous insertion of the cord was associated with an increased risk of PROM (OR 1.6, 95% CI 1.5-1.7), pPROM (OR 2.7, 95% CI 2.4-3.0), SPTB (OR 2.0, 95% CI 1.9-2.2), and a short cord (OR 1.7, 95% CI 1.5-1.8). Marginal insertion was to a lesser extent associated with these complications. Occurrences of SPTB and anomalous insertion declined. The decline in SPTB persisted after including an interaction term between anomalous insertion and time.Velamentous and, to a lesser extent, marginal cord insertions were associated with increased risk of PROM, pPROM, SPTB, and short cord. This suggests a common pathogenesis behind altered function of the membranes, cord, and placenta. The decline in SPTB could not be explained by the reduction in the occurrence of anomalous cord insertion.

OBJECTIVE To test whether adding conditional growth centiles to size centiles of estimated fetal weight (EFW) improves prediction of adverse perinatal outcome in pregnancies with or at risk of having a small-for-gestational-age (SGA) fetus. METHODS This prospective longitudinal study included pregnant women at risk of or diagnosed with an SGA (≤ 5(th) centile) fetus. They underwent serial ultrasound measurements and the final two were included in the analyses for this study. The EFW was categorized into normal (> 5(th) or 10(th) centile) and abnormal (≤ 5(th) or 10(th) centile) for size and conditional growth before entering the variables into log-binomial regression analyses. Adverse outcomes were delivery

To assess whether anomalous cord insertion is associated with risk of complications in the third stage of labor.A population-based study.Norwegian Medical Birth Register.All singleton births (gestational age16 weeks and45 weeks) during the period 1999-2011 (n = 738,443 singletons). Deliveries by cesarean were excluded, leaving 628,680 vaginal singleton deliveries for the analyses.Calculation of odds ratios for complications in the third stage of labor (postpartum hemorrhage, manual delivery of the placenta, curettage) in velamentous and marginal cord insertion by logistic regression with adjustment for confounders.Complications in the third stage of labor, postpartum hemorrhage, manual placental removal and curettage.Anomalous cord insertion was associated with an increased risk of complications in the third stage of labor, the risk being higher for velamentous than for marginal insertion. The risks persisted after adjusting for possible confounding factors. Velamentous cord insertion carried a 5.6% risk of a need for manual removal of the placenta, compared with the risk of 1.1% for nonvelamentous insertion (odds ratio = 5.21, 95% confidence interval 4.71-5.76) in vaginal delivery, and we found increased risks of curettage (odds ratio = 3.29, 95% confidence interval 2.87-3.77) and postpartum hemorrhage (odds ratio = 2.06, 95% confidence interval 1.77-2.39).Marginal and especially velamentous cord insertion is associated with an increased risk of hemorrhage in the third stage of labor, need for manual removal of the placenta and curettage. Anomalous cord insertion can be identified prenatally and so possibly influence obstetric management.

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 determine the association between 5-min Apgar score and umbilical cord artery carbon dioxide tension (pCO2). Design. Observational study. Setting. European hospital labor wards. Population. Data from 36 432 newborns � 36 gestational weeks were obtained from three sources: two trials of monitoring with fetal electrocardiogram (the Swedish randomized controlled trial and the European Union Fetal ECG trial) and M€ Hospital data. After validation of the acid–base values, 25 806 5-min Apgar scores were available for analysis. Methods. Validation of the umbilical cord acid–base values was performed to obtain reliable data. 5-min Apgar score was regressed against cord artery pCO2 in a polynomial multilevel model. Main outcome measures. Five-min Apgar score, umbilical cord pCO2, pH, and base deficit. Results. Overall, a higher cord artery pCO2 was found to be associated with lower 5-min Apgar scores. However, among newborns with moderate acidemia, lower umbilical cord artery pCO2 ( � median pCO2 for the specific cord artery pH) was associated with lower 5-min Apgar scores, with a relative risk of 2.0 (95% confidence interval: 1.4–2.8) for 5-min Apgar scores 0–6. Conclusions. Metabolic acidosis affects the newborn’s vitality more than respiratory acidosis. In addition, elevated levels of pCO2 may be beneficial for fetuses with moderate acidemia, and thus cord artery pCO2 is a factor that should be considered when assessing the compromised newborn. Abbreviations: AUC, area under the curve; BDecf, base deficit in the extracellular fluid; CI, confidence interval; CTG, cardiotocography; EU-STAN, European Union Fetal electrocardiogram multicenter trial; pCO2, carbon dioxide tension; ROC, receiver operating characteristic; SRCT, Swedish randomized controlled trial on intrapartum fetal monitoring; STAN, CTG with automatic ST-interval analysis of the fetal electrocardiogram.

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.

Introduction. Centiles of middle cerebral artery pulsatility index and cerebroplacental ratio are useful for predicting adverse perinatal outcomes. A ‘conditional centile’ is conditioned by a previous measurement reflecting degree of individual change over time. Here we test whether such centiles are independent predictors and whether their combination improves prediction. Material and methods. This prospective longitudinal study included 220 pregnant women diagnosed with or at risk of having a small-for-gestational-age fetus. Serial Doppler measurements of the umbilical artery and middle cerebral artery pulsatility indexs were used to calculate cerebroplacental ratio. Preterm birth, operative delivery due to fetal distress, admission to neonatal intensive care unit, 5-min Apgar score

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.

OBJECTIVE: To assess whether premature rupture of membranes (PROM) is associated with placental abruption. DESIGN: Population-based study. SETTING: Data were extracted from the Medical Birth Registry of Norway. POPULATION: All women with PROM (18,889 cases), including 3,077 cases of preterm premature rupture of membranes (p-PROM), among a total of 355 416 singleton births in Norway during 1999-2005 with gestational age 17-44 weeks. METHODS: Logistic regression was used to assess whether placental abruption was associated with PROM in preterm and term births. MAIN OUTCOME MEASURES: Placental abruption. RESULTS: The occurrence of placental abruption in p-PROM was higher than in the total study population, 11.0 per 1,000 (34 of 3 077) vs. 4.2 per 1 000 (1 495 of 355 416; adjusted odds ratio 2.6, 95% confidence interval 1.8-3.7). Restricting the analyses to preterm births, the occurrence of placental abruption was less in p-PROM (11.0 per 1,000) than in births without p-PROM (36.1 per 1 000; adjusted odds ratio 0.3, 95% confidence interval 0.2-0.4). In term births, no statistically significant association was observed. CONCLUSIONS: The findings suggest that in p-PROM the risk of placental abruption is not higher than in other preterm births; rather the opposite. However, comparing the risks in p-PROM and the total gestational age range, the present study confirmed results reported in previous studies of a higher risk of placental abruption in p-PROM than in the total birth population.

Objective. To study the association between maternal weight gain in pregnancy and fetal abdominal circumference in the second trimester. Design. Prospective cross-sectional study. Setting. Low-risk antenatal clinic. Population. Six hundred and fifty women with low-risk pregnancy. Methods. Women with a regular menstrual period (28±4 days) and certain information on the last menstrual period were recruited when they were referred for routine ultrasound scanning. Women with a discrepancy of> 14 days between ultrasound and menstrual age were excluded. Maternal weight gain during pregnancy was derived from information in the antenatal chart and the weekly weight gain was calculated. Fetal abdominal circumference measurements were registered in gestational weeks 15-25 and their z-scores, together with the z-scores of maternal weight gain, were used in a linear regression analysis. Main outcome measures. Association between maternal weight gain and fetal abdominal circumference. Results. Based on the complete data of 515 women we found a mean maternal weight gain during pregnancy of 0.39kg/week and a positive association between this weight gain and fetal abdominal circumference in the second trimester (r=0.122 (95%CI 0.051-0.194)), with the strongest effect in women with the slowest weight gain (

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.

Objectives In humans, fetal breathing movements affect blood velocities in the umbilical vein and artery, but it is not known whether fetal respiratory activity is associated with increased fetal blood flow through the placenta. We therefore tested this hypothesis in the present study. Methods One-hundred and ten women with low-risk singleton pregnancies were each examined three times by ultrasound during the second half of pregnancy. Fetal heart rate, umbilical artery blood velocity, umbilical vein diameter and blood velocity, and umbilical blood flow at the placental end were determined during fetal rest and fetal respiratory movements. Results Based on 330 observations obtained during fetal rest or breathing activity, no difference was found in the mean fetal heart rate (beats per minute (bpm)) during rest compared with breathing (142 bpm vs. 142 bpm, respectively). Although fetal breathing affected the umbilical artery waveform, there was no difference in the mean time-averaged maximum velocity between rest and breathing: 26.6 (95% CI, 25.1–28.3) cm/s vs. 28.9 (95% CI, 27.2–30.7) cm/s, respectively. The umbilical vein was 27% greater in cross-sectional area and the blood velocity 9% higher during breathing, resulting in a 42% increase in mean umbilical blood flow: 121.8 (95% CI, 109.5–135.0) mL/min at rest vs. 173.0 (95% CI, 158.0–188.6) mL/min during breathing. Venous velocity was calculated from recordings of mean duration 3.7 s at rest and 6.2 s of respiratory activity. Gestational age did not influence the relationship. Conclusion Fetal breathing is associated with increased umbilical blood flow during the second half of pregnancy. Umbilical vein distension during breathing suggests active endocrine regulation. Copyright © 2010 ISUOG. Published by John Wiley & Sons, Ltd.

Objectives Toestablishreferencerangessuitableforserial assessments of the fetal middle cerebral (MCA) and umbilical (UA) artery blood flow velocities, pulsatility index (PI) and cerebroplacental pulsatility ratio and to provide terms for calculating conditional reference intervals suitable for individual serial measurements. Methods This was a longitudinal study of 161 singleton pregnancies. Using Doppler ultrasound, MCA and UA blood velocities and PI were determined three to five times at 3‐5-week intervals over a gestational age range of 19‐41 weeks. Polynomial regression lines for the 95 th ,5 0 th and 5 th percentiles were calculated for the peak systolic velocity (PSV), time-averaged maximum velocity (TAMXV), PI and cerebroplacental ratio. Terms for calculating conditional reference intervals were established. Results Based on 566 observations our new longitudinal reference ranges for fetal middle cerebral PSV, TAMXV and PI provided terms for calculating conditional reference intervals (i.e. predicting expected 95% confidence limits based on a previous measurement), and correspondingly for the cerebroplacental ratio (n = 550). The reference ranges were at some variance with those of previous cross-sectional studies. The narrow 95% confidence limits for the 5 th and 95 th percentiles ensured reliable ranges. Conclusions We have established longitudinal reference rangesappropriatefortheserialassessmentofMCAblood velocities and PI and cerebroplacental ratio. Particularly the terms for calculating conditional ranges based on a previous observation make this system more appropriate for longitudinal monitoring than are cross-sectional data.

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.

OBJECTIVES: Serial Doppler measurements of the ductus venosus are used increasingly for monitoring fetuses at risk of hemodynamic compromise, but existing reference ranges are based on cross-sectional studies and thus are less suitable for comparison with serial measurements. We aimed to establish longitudinal reference ranges for ductus venosus flow velocities and waveform indices and to provide the necessary terms for calculating conditional reference ranges for serial measurements. METHODS: This was a longitudinal study of 160 low-risk pregnancies. Pulsed Doppler ultrasound was used to record ductus venosus blood flow velocities at 4-week intervals from 20-22 weeks of gestation onwards. RESULTS: With a success rate of 93%, 547 measurements (four or five in each fetus) were used to establish reference ranges. The time-averaged maximum velocity was 50 cm/s at 21 weeks of gestation, increased to 60 cm/s at 32 weeks, and remained so until term. Similarly, the peak systolic velocity increased from 59 cm/s at 21 weeks to 71 cm/s at 31 weeks and remained so until term. The end-diastolic velocity showed a continuous increase from 31 cm/s at 21 weeks to 43 cm/s at 40 weeks. The pulsatility index for veins decreased from 0.57 at 21 weeks to 0.44 at 40 weeks. When conditioned by a previous measurement, the reference ranges for the next observation became narrower and commonly shifted compared with those of the entire population. CONCLUSION: The new longitudinal reference ranges presented here reflect the development of the ductus venosus flow velocities and velocity indices and are thus appropriate for serial measurements, particularly if conditional terms are included

Objective To determine the degree of ductus venosus (DV) shunting in fetuses with intrauterine growth restriction (IUGR) and the effect of various degrees of umbilical circulatory compromise. Methods This was a cross-sectional observational study. Sixty-four fetuses with IUGR (estimated weight ≤ 2.5th percentile) underwent ultrasound examination. The diameter, velocity, and blood flow were determined in the DV and intra-abdominal umbilical vein (UV), and the fraction of shunting and DV : UV diameter ratios were calculated. Placental compromise was classified according to either normal umbilical artery (UA) pulsatility index (PI), UA-PI > 97.5th percentile, or absent or reversed end-diastolic flow velocity (A/REDV). Regression analysis was used to construct mean values, and SD scores were used to determine differences compared with a reference population (n = 212) after ln- or power-transformation. Results In the 64 growth-restricted fetuses, the average DV shunting was 39% compared with 25% in the reference group (overall P 97.5th percentile, and A/REDV were 31%, 35%, and 57%, respectively. Fetuses with IUGR and normal UA-PI (SD score: mean, 0.48; 95% CI, 0.04–0.92) did not shunt significantly more than did the reference fetuses (SD score: mean, 0.0; 95% CI, − 0.15 to 0.15), but those with UA-PI > 97.5th percentile (SD score: mean, 0.85; 95% CI, 0.41–1.29), and particularly those with A/REDV (SD score: mean, 1.56; 95% CI, 1.0–2.12) did shunt significantly more. With more DV shunting, these fetuses distributed correspondingly less umbilical blood to the liver, one of the mechanisms being a lower perfusion pressure as reflected in the lower DV blood velocity (P < 0.0001). Conclusions DV shunting is higher and the umbilical blood flow to the liver is less in fetuses with IUGR, particularly in those with the most severe umbilical hemodynamic compromise. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.

Background. The aim of the present study is to establish new reference charts for gestational age assessment based on fetal femur length (FL), and new reference ranges for FL to head ratios at gestational weeks 10-25, and to determine the effect of maternal and fetal factors on these charts. Methods. Six hundred fifty low-risk women with regular menstrual periods and singleton pregnancies were recruited to a prospective cross-sectional study after obtaining written consent. FL, outer-outer biparietal diameter (BPD), and head circumference (HC) were measured at 10-25 weeks of gestation. We used regression analysis in order to construct mean curves and to assess the effect of maternal and fetal factors on age assessment. Results. The new chart for age assessment by means of FL was based on 636 measurements. The 95% CI of the mean corresponded to

Background: Maternal height and weight have increased during the past 20 years, as has birthweight. The aim of the present study was to establish new reference charts for gestational age (GA) assessment using fetal biparietal diameter (BPD) and head circumference (HC), and to determine the effect of maternal and fetal factors on age assessment. Methods: This was a prospective, cross-sectional study of 650 healthy women with regular menstrual periods and singleton uncomplicated pregnancies, recruited after written consent. BPD (outer-outer) and HC were measured at 10-24 weeks of gestation. We used regression analysis to construct mean curves and assess the effect of maternal and fetal factors on age assessment. Results: BPD and HC were successfully measured in 642 participants. Using BPD and HC before 20 weeks, the new charts gave 3-8 days higher GA assessment than the charts presently in use, and

Objective In animal experiments hypoxemia induces an increased shunting through the fetal foramen ovale (FO). Based on the hypothesis that the FO is expanded to permit more flow, the aim of this study was to determine the size of the FO in growth-restricted human fetuses. Methods Thirty-one women with singleton pregnancies complicated with growth-restriction (< 5th percentile) were examined at 24–39 weeks of gestation. The diameter between the FO valve and the atrial septum was determined during maximum excursion in a horizontal transverse section of the fetal heart, and the transverse diameter of the right atrium (RA) was noted. The pulsatility index (PI) was determined in the umbilical artery (UA) and absent or reversed end-diastolic flow velocity was noted. The measurements were compared with a reference population using Z-scores. Results In comparison with normally grown fetuses, the growth-restricted fetuses had a normal RA size (P = 0.08) but a smaller FO (P = 0.002), particularly when expressed as a relative size by the ratio FO/RA (P < 0.0001). This effect on the FO and FO/RA was seen mainly at < 32 weeks of gestation (P = 0.003 and P < 0.0001, respectively), and was not significant later in pregnancy. There was a tendency towards a negative relationship between relative size of the FO (FO/RA) and progressive placental compromise (overall P < 0.0001). Conclusions Growth-restricted fetuses maintain a normally grown heart (expressed by the RA diameter) but a reduced FO diameter. The effect is seen before 32 weeks and tends to be more marked in fetuses with pronounced hemodynamic compromise of the placenta. This supports the theory that FO shunting is impaired in severely premature fetuses with placental compromise. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.

Objectives Umbilical venous pulsation is an important sign of hemodynamic compromise, but is also found under normal physiological conditions. Mathematical modeling suggests that vascular compliance is a determinant for pulsation, and we tested this by studying velocity pulsation at three sites on the umbilical vein. Methods In a cross-sectional study of 279 low-risk pregnancies (20–40 weeks' gestational age) blood flow velocity in the umbilical vein was determined before, within and after the umbilical ring in the fetal abdominal wall, and the incidence and magnitude of pulsation (the difference between the maximum and minimum velocity during a pulse, and pulsatility index) were noted. Based on the fact that the vessel cross-sectional area is an important determinant of compliance, we measured the diameter and time-averaged maximum velocity to reflect variation in diameter and compliance at the three sites. Results The incidence of umbilical venous pulsation was higher at the umbilical ring in the abdominal wall (242/279, 87%, 95% CI 82–90) than in the cord (43/198, 22%, 95%CI 16–27) or intra-abdominally (84/277, 30%, 95% CI 25–36) (P < 0.001). When pulsation was observed intra-abdominally, the pulsatility was not different from that at the umbilical ring (P = 0.16). However, the lowest pulsatility was found in the cord vein (P < 0.0001), where the largest vein diameter was found. Conclusion The high incidence of venous pulsation at the umbilical ring where diameter and compliance are low supports the suggestion that local compliance is an important factor influencing pulsation in fetal veins. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.

Objective. To validate the diagnosis of an unexplained antepartum fetal death in the Medical Birth Registry of Norway against data obtained from hospital records, alone and combined with autopsy data. To compare epidemiologic characteristics of an unexplained fetal death based on cases recorded by the three data sources. Methods. Data on unexplained fetal deaths in the Registry were compared with clinical and autopsy data from 108 457 singletons with a gestational age ≥ 28 weeks or a birthweight ≥ 1000 g delivered in 1985-97 at Haukeland Hospital in Bergen and Aker Hospital in Oslo. Results. Compared with clinical data, the positive and negative predictive values of a Registry diagnosis of an unexplained fetal death were 88% and 86%, respectively, while the sensitivity and specificity were 76% and 93%, respectively. Compared with clinical and autopsy data combined, the positive and negative predictive values of a Registry diagnosis of an unexplained fetal death were 77% and 89%, respectively, while the se...

Background. It is common to admit to hospital or start intensive ambulatory antenatal care of pregnant women with a previous placental abruption using the gestational age of the previous placental abruption as a starting point. In some instances, close surveillance may be commenced much earlier. There is no consensus when in a subsequent pregnancy such measures should be initiated. Objective. The analyses aimed at the prevention of complicated (preterm, small for gestational age, or perinatal death) recurrent placental abruptions, assessing at which time in a subsequent pregnancy special surveillance should start in order to anticipate and prevent a recurrence. Design. A cohort study based on the Medical Birth Registry of Norway. Calculation of gestational age specific risks of placental abruption in a second pregnancy and estimation of when to initiate surveillance in order to reduce an increased risk of recurrent placental abruption to the initial level of initial abruption in the second pregnancy. Resu...

Objectives Based on the assumption that the horizontal area between the fetal foramen ovale valve and the atrial septum (the outlet) represents the limiting structure for the foramen ovale flow, our objective was to determine the normal size of this section during the second half of pregnancy. Methods One hundred and thirty-eight women with low-risk singleton pregnancies were examined in a cross-sectional study between 18 and 42 weeks of gestation. Using ultrasound imaging and M-mode, the area and diameter between the foramen ovale valve and the atrial septum were determined in a four-chamber view of the fetal heart above the foramen ovale limbus. The inferior vena cava cross section and right atrial width were also determined. Results The mean foramen ovale width increased from 3 mm at 18 weeks to 6 mm at term. Correspondingly, the horizontal area grew from 15 to 50 mm2. The mean ratio between this area and the area of the inferior vena cava fell from 1 at 18 weeks to 0.5 at term. The ratio between the transverse width of the foramen ovale and the right atrium remained at average 0.45–0.50 until 32 weeks, when a slight reduction was observed towards term. Conclusions Normal values for the horizontal cross section and transverse diameter of the foramen ovale outlet were established for the second half of pregnancy. In particular, the horizontal transverse diameter and its ratio to the right atrial width are easy to determine, and use of these measurements is thus suggested for the assessment of the fetal foramen ovale. Copyright © 2001 International Society of Ultrasound in Obstetrics and Gynecology

Objectives. To assess secular trends in mortality rates in breech presentation in Norway and the effects of gestational age, birth defects and delivery method. Material and methods. The Medical Birth Registry of Norway 1967-1994, with 45,579 breech presentation births from 24 weeks of gestation onwards, with mortality rate comprising all stillbirths from 24 completed weeks of gestation and all neonatal deaths (extended peri- and neonatal mortality) as main outcome variable. Results. The extended peri- and neonatal mortality rate in breech presentation births declined during the study period from 9.2% in 1967-76 to 5.5% in 1977-86 and to 3.0% in 1987-94. The highest relative risk of mortality in breech presentation versus the total birth population was observed in intrapartum death and in mortality less than 24 hours after delivery. Stillbirth represented about half of the extended peri- and neonatal mortality throughout the study period. Also in infants with birth defects, the survival increased during th...

Objective. To assess the risk of small for gestational age (SGA), preterm birth, pregnancy induced hypertension (PIH), and perinatal death in the pregnancy immediate subsequent to a placental abruption (PA) in the same mother. Design. A cohort study based on the Medical Birth Registry of Norway. Results. Odds ratios of SGA in subsequent PA- and non-PA deliveries were 2.8 (absolute risk = 18.5%) and 2.0 (13.9%), respectively, compared with non-PA deliveries without a history of previous PA among siblings (7.5%) after exclusion of cases with SGA in the immediate previous birth. After exclusion of cases with spontaneous preterm birth in the immediate previous delivery, odds ratios of spontaneous preterm birth in subsequent PA- and non-PA deliveries were 17.0 (36.3%) and 2.1 (6.6%), compared with non-PA deliveries without a history of previous PA among siblings (3.2%). After exclusion of cases with PIH in the immediate previous pregnancy, odds ratios of PIH in subsequent PA- and non-PA pregnancies were 2.9 (6...

Objective. To evaluate secular trends in the occurrence of placenta previa and whether placenta previa is associated with the outcome of previous pregnancies, cesarean section, and sociodemographic factors. Design. A cohort study based on the Medical Birth Registry of Norway. Placenta previa in the second pregnancy was investigated for associations with outcomes in the first pregnancy and sociodemographic factors. Results. In birth orders 1 and 2 the occurrence of placenta previa was 1.2 and 2.2 per 1000, respectively, with no secular trend. The occurrence increased with maternal age and was lowest in women aged 20-29 years. The recurrence rate was 23 per 1000 (adjusted odds ratio (OR) of recurrence=9.7). In women with prior delivery at ≤25 gestational weeks the risk of placenta previa was 6.7 per 1000 (adjusted OR=3.0). In women with prior placental abruption the risk was 5.8 per 1000 (OR=2.6). In women with prior perinatal death the risk was 4.4 per 1000 (adjusted OR=1.8). No independent relationship em...

Blood flow measurement in the fetus is susceptible to substantial error. Increased numbers of measurements can improve the precision. To quantify this, we assessed how the number of ultrasound measurements affected the calculation of individual mean diameters of fetal veins. A study of the umbilical vein (UV) and ductus venosus (DV) was carried out in 167 pregnancies in a clinical setting. The UV diameter was measured 2–13 times in 163 participants and the DV for the same number of times in 158. A one-way analysis of variance gave mean within-subject SD of 0.23 mm for the UV (diameter 2.0–8.0 mm) and 0.17 mm for the DV (diameter 0.3–2.3 mm). The 95% limit for the within-subject mean diameter calculated from two, four, six and ten measurements of the UV were 0.31, 0.22, 0.18 and 0.14 mm, respectively. For the DV the corresponding results were 0.23, 0.16, 0.13 and 0.10 mm. The study shows how increasing the number of measurements to calculate a mean diameter substantially improves the precision of vascular cross-section assessment. The limitation of the method is expressed in the exponential increase in numbers needed to achieve further improvement. Copyright © 1998 International Society of Ultrasound in Obstetrics and Gynecology

Background. To study factors influencing delivery method in breech presentation. Methods. Population based cohort study from The Medical Birth Registry of Norway, comprising all singleton deliveries in Norway, 1967-1994, 1,592,064 deliveries of which 45,921 (2.9%) were in breech presentation. Results. The proportion of cesarean section in breech presentation increased from 3.6 per 100 in 1969 to 58.8 in 1994. The relative risk for delivery by cesarean section in breech presentation compared to the nonbreech population increased from 2.0 (95% CI 1.5-2.7) in 1967 to 5.9 (95% CI 5.6-6.2) in 1994. It declined by maternal age, increased by gestational age and was lowest among mothers with urban residence. A negative association was observed between the annual number of births at the delivery department and the cesarean section proportion. However, during the observation period, the centralization of breech deliveries to the largest departments was reduced. Conclusions. Vaginal delivery in breech presentation was particularly observed in large delivery departments and among mothers with urban residence. Since experience and practical competence are prerequisites for successful vaginal delivery, this centralization seems justified. Further centralization of all breech presentation births should be pursued. However, preparedness as to vaginal delivery should be established also at the smaller units, e.g. by a routine providing periodical centralized training for obstetricians working in smaller institutions.

Background. To study the occurrence of breech presentation and its association with demographic and geographic variables. Method. Population based cohort study from the Medical Birth Registry of Norway comprising all singleton deliveries 1967-1994, a total of 1,592,064 deliveries. Of these, 45,921 in breech presentation. Results. From 1967 through 1994, the breech presentation proportion increased from 2.2%, (95% CI 2.1-2.3) to 3.4% (95% Cl 3.2-3.5). Breech presentation was associated with high maternal age and low birth order, as well as low gestational age and birthweight. The secular trend was mainly due to demographic changes in terms of increasing proportions of births with low birth order and high maternal age. Breech presentation was most frequent in urban areas. Conclusions. Strong associations were observed between breech presentation and low birth order as well as high maternal age. The findings are compatible with both intrinsic as well as environmental mechanisms. A full understanding of the birth order effect necessitates further studies based on sibship data. Prevention of premature delivery would be an effective measure for reducing the breech presentation proportion.

To study secular trends of placental abruption (PA), the effects of demographic variables and the use of cesarean section (CS) associated with PA.A population based cohort study.The Medical Birth Registry of Norway.9,592 cases of PA of a total of 1,446,154 births notified, i.e. all births in Norway 1967-1991.The PA proportion was 6.6 per 1000 births of a gestational age of 16 weeks or more, ranging from 5.3 in 1971 to 9.1 in 1990. Birth order two had the lowest proportion and it increased by maternal age. The PA proportion decreased by gestational age from 86.4 per 1000 below 28 weeks to 3.4 in term pregnancies. The PA proportion per 10,000 pregnancies at risk increased from 1.3 in the 28th week to 14.1 in the 42nd week. A secular trend of a decreasing but still high relative risk of PA in SGA-births at any gestational age increased from 1967 through 1991. The relative risk of PA of Apgar score7 after five minutes, adjusted for gestational age, was 7.8.Inspite of an increasing CS rate, an increasing proportion of PA was noted from 1967 through 1991. The proportion was lowest for birth order two and increased by maternal age. To an increasing extent, PA births were centralized. SGA, prematurity and asphyxia were major problems associated with PA. A tendency towards larger infants and a decreasing relative risk of PA in SGA-births might be attributable to improvements in antenatal care.

The computerized records of a population of 7214 women who were delivered during the period 1987-1991 were analysed. We studied the possible relationship of the duration of the first and second stages of labor to maternal age. In para 0, para 1 and para 2+ mothers we found an independent positive correlation between the second stage duration and maternal age. By multiple stepwise regression analysis maternal age turns out to be one of the most influential maternal characteristics of the second stage of labor. No correlation was found between maternal age and the duration of the first stage.