Medical Birth Registry Of Norway Research Articles

Hypertensive disorders of pregnancy among women with cardiovascular disease in Norway: A historical cohort study.

Women with cardiovascular disease may be at increased risk of hypertensive disorders of pregnancy (HDP). We aimed to: (1) Investigate the occurrence of HDP in a cohort of pregnant women with cardiovascular disease and compare it with the occurrence in the general population. (2) Assess the association between maternal cardiovascular risk and risk of HDP. We reviewed clinical data on a cohort of 901 pregnancies among 708 women with cardiovascular disease who were followed at the National Unit for Pregnancy and Heart Disease and gave birth at Oslo University Hospital between 2003 and 2018. The exposure under study was maternal cardiovascular risk, classified as low, moderate, or high based on a modified classification by the World Health Organization. The main outcome of interest was HDP, which included pre-eclampsia and gestational hypertension. The proportion of HDP cases in the general population in the same period was extracted from the Medical Birth Registry of Norway. We used logistic regression to estimate crude and adjusted odds ratios (OR) of HDP, with associated 95% confidence intervals (CIs), for women with moderate- and high cardiovascular risk compared to women with low risk. The occurrence of HDP in the study cohort was 12.1% (95% CI: 10.0%-14.4%) and varied between 8.7% (95% CI: 6.5%-11.3%) in the low-risk group, 15.7% (95% CI: 11.1%-21.4%) in the moderate-risk group, and 22.2% (95% CI: 15.1%-30.8%) in the high-risk group. By contrast, the nationwide occurrence of HDP was 5.1% (95% CI: 5.1%-5.2%). In the study cohort, the proportions of pregnancies with gestational hypertension and pre-eclampsia were similar (6.3% and 5.8%, respectively). Compared to pregnancies with low cardiovascular risk, the adjusted OR of HDP was 2.04 (95% CI: 1.21-3.44) in the moderate-risk group and 2.99 (95% CI: 1.73-5.18) in the high-risk group. The occurrence of hypertensive disease of pregnancy in the study cohort was more than doubled compared to the general population in Norway. The risk of HDP increased with maternal cardiovascular risk group. We recommend taking into account maternal cardiovascular risk group when assessing risk and prophylaxis of HDP.

Preterm birth, preeclampsia, gestational hypertension and offspring birth weight in women with active juvenile idiopathic arthritis and healthy controls

ObjectivesThere is insufficient knowledge about pregnancy outcomes in women with juvenile idiopathic arthritis (JIA). Our objective was to explore a possible association of inflammatory active JIA and pregnancy outcomes, including preterm birth, preeclampsia, gestational hypertension, and offspring gestational weight.MethodsWe linked data from the Norwegian nationwide observational register RevNatus with data from the Medical Birth Registry of Norway (MBRN) for the period 2010 to 2019. Singleton births in women with JIA (n = 181) included in RevNatus were cases. After excluding births in mothers with rheumatic inflammatory diseases, the remaining singleton births registered in MBRN, served as population controls (n = 575 798).ResultsPreterm birth was more frequent in women with active JIA (17.6%) and of equivalent frequency in women with inactive JIA (3.1%), compared to population controls (4.9%). Preeclampsia had similar rates in women with JIA and population controls while gestational hypertension was more frequent in women with active JIA (7.2%) and inactive JIA (6.9%) compared to population controls (1.7%). Abnormal fetal growth occurred in similar rates in women with JIA and population controls.ConclusionHaving active JIA in pregnancy increased the risk for preterm birth (risk difference 12.7, 95% CI 4.7 to 25.3) and gestational hypertension (risk difference 6.2, 95% CI 1.4 to 16.8). There was no increased risk for preeclampsia or abnormal fetal growth compared to population controls.

Heterogeneity in the risk of cardiovascular disease mortality after the hypertensive disorders of pregnancy across mothers' lifetime reproductive history.

Prior studies on maternal cardiovascular disease (CVD) mortality and hypertensive disorders of pregnancy (HDP) have focused only on a woman's first birth and have not accounted for successive affected pregnancies. The objective of this study is to identify mothers' risk of CVD mortality considering lifetime reproductive history. We used data from the Medical Birth Registry of Norway, the Norwegian Cause of Death Registry, and the Norwegian National Population Register to identify all mothers who gave birth from 1967 to 2020. Our outcome was mothers' CVD death before age 70. The primary exposure was the lifetime history of HDP. The secondary exposure was the order of HDP and gestational age at delivery of pregnancies with HDP. We used Cox regression models to estimate hazard ratio (HR) and 95% confidence interval (CI), adjusting for education, mother's age, and year of last birth. These models were stratified by the lifetime number of births. Among 987,378 mothers, 86,294 had HDP in at least one birth. The highest CVD mortality, relative to mothers without HDP, was among those with a pre-term HDP in their first two births, although this represented 1.0% of mothers with HDP (HR 5.12, 95% CI 2.66, 9.86). Multiparous mothers with term HDP in their first birth only had no increased risk of CVD relative to mothers without HDP (36.9% of all mothers with HDP; HR 1.12, 95% CI 0.95, 1.32). All other mothers with HDP had a 1.5- to 4-fold increased risk of CVD mortality. This study identified heterogeneity in the risk of CVD mortality among mothers with a history of HDP. A third of these mothers are not at higher risk compared to women without HDP, while some less common patterns of HDP history are associated with severe risk of CVD mortality.

Parental genetically predicted liability for coronary heart disease and risk of adverse pregnancy outcomes: a cohort study

BackgroundAdverse pregnancy outcomes (APO) may unmask or exacerbate a woman’s underlying risk for coronary heart disease (CHD). We estimated associations of maternal and paternal genetically predicted liability for CHD with lifelong risk of APOs. We hypothesized that associations would be found for women, but not their male partners (negative controls).MethodsWe studied up to 83,969‬ women (and up to 55,568‬ male partners) from the Norwegian Mother, Father and Child Cohort Study or the Trøndelag Health Study with genotyping data and lifetime history of any APO in their pregnancies (1967–2019) in the Medical Birth Registry of Norway (miscarriage, stillbirth, hypertensive disorders of pregnancy, gestational diabetes, small for gestational age, large for gestational age, and spontaneous preterm birth). Maternal and paternal genetic risk scores (GRS) for CHD were generated using 148 gene variants (p-value < 5 × 10−8, not in linkage disequilibrium). Associations between GRS for CHD and each APO were determined using logistic regression, adjusting for genomic principal components, in each cohort separately, and combined using fixed effects meta-analysis.ResultsOne standard deviation higher GRS for CHD in women was related to increased risk of any hypertensive disorders of pregnancy (odds ratio [OR] 1.08, 95% confidence interval [CI] 1.05–1.10), pre-eclampsia (OR 1.08, 95% CI 1.05–1.11), and small for gestational age (OR 1.04, 95% CI 1.01–1.06). Imprecise associations with lower odds of large for gestational age (OR 0.98, 95% CI 0.96–1.00) and higher odds of stillbirth (OR 1.04, 95% CI 0.98–1.11) were suggested. These findings remained consistent after adjusting for number of total pregnancies and the male partners’ GRS and restricting analyses to stable couples. Associations for other APOs were close to the null. There was weak evidence of an association of paternal genetically predicted liability for CHD with spontaneous preterm birth in female partners (OR 1.02, 95% CI 0.99–1.05), but not with other APOs.ConclusionsHypertensive disorders of pregnancy, small for gestational age, and stillbirth may unmask women with a genetically predicted propensity for CHD. The association of paternal genetically predicted CHD risk with spontaneous preterm birth in female partners needs further exploration.

Male patients with inflammatory joint diseases are less likely than controls to be childless: results from a Norwegian population-based cohort study of 10 865 patients

ObjectivesTo investigate the number of children per man and the proportion of childless men as a proxy of fertility in a national cohort of men with inflammatory joint diseases (IJDs),...

Shoulder dystocia by severity in families: A nationwide population study.

Previous studies have established a history of shoulder dystocia as an important risk factor for shoulder dystocia, but studies on shoulder dystocia by severity are scarce. It is unknown if shoulder dystocia tends to be passed on between generations. We aimed to assess the recurrence risk of shoulder dystocia by severity in the same woman and between generations on both the maternal and paternal side. We also assessed the likelihood of a second delivery and planned cesarean section after shoulder dystocia. This was a population-based cohort study, using data from the Medical Birth Registry of Norway. To study recurrence in the same mother, we identified 1 091 067 pairs of first and second, second and third, and third and fourth births in the same mother. To study intergenerational recurrence, we identified an individual both as a newborn and as a mother or father in 824 323 mother-offspring pairs and 614 663 father-offspring pairs. We used Bayesian log-binomial multilevel regression to calculate relative risks (RR) with 95% credible intervals. In subsequent deliveries in the same woman the unadjusted RR of recurrence was 7.05 (95% credible interval 6.39-7.79) and 2.99 (2.71-3.31) after adjusting for possible confounders, including current birthweight. The RRs were higher with severe shoulder dystocia as exposure or outcome. With severe shoulder dystocia as both exposure and outcome, unadjusted and adjusted RR was 20.42 (14.25-29.26) and 6.29 (4.41-8.99), respectively. Women with severe and mild shoulder dystocia and those without had subsequent delivery rates of 71.1, 68.9 and 69.0%, respectively. However, the rates of planned cesarean section in subsequent deliveries for those without shoulder dystocia, mild and severe were 1.3, 5.2 and 16.0%, respectively. On the maternal side the unadjusted inter-generational RR of recurrence was 2.82 (2.25-3.54) and 1.41 (1.05-1.90) on the paternal side. Corresponding adjusted RRs were 1.90 (1.51-2.40) and 1.19 (0.88-1.61), respectively. We found a strong recurrence risk of shoulder dystocia, especially severe, in subsequent deliveries in the same woman. The inter-generational recurrence risk was higher on the maternal than paternal side. Women with a history of shoulder dystocia had more often planned cesarean section.

Unveiling sex bias and adverse neonatal outcomes in ultrasound estimation of gestational age: A population-based cohort study.

Gestational age estimation by second-trimester ultrasound biometry introduces systematic errors due to sex differences in early foetal growth, consequently increasing the risk of adverse neonatal outcomes. Ultrasound estimation earlier in pregnancy may reduce this bias. To investigate the distribution of sex ratio by gestational age and estimate the risk of adverse outcomes in male foetuses born early-term and female foetuses born post-term by first- and second-trimester ultrasound estimations. This population-based study compared two cohorts of births with gestational age based on first- and second-trimester ultrasound in the Medical Birth Registry of Norway between 2016 and 2020. We used a log-binomial regression model to estimate adjusted relative risk (RR) with 95% confidence interval (CI) for Apgar score <7 at 5 min, umbilical artery pH <7.05, neonatal intensive care unit (NICU) admission and respiratory morbidity in relation to foetal sex. The sex ratio at birth in gestational weeks 36-43 showed less male predominance in pregnancies estimated in first compared to second trimester. Any adverse outcome was registered in 627 of 4470 male infants born in gestational weeks 37-38 and 618 of 6406 females born ≥41 weeks. Male infants born in weeks 37-38 had lower risk of NICU admission (RR 0.76, 95% CI 0.58, 0.99), Apgar score <7 at 5 min (RR 0.63, 95% CI 0.28, 1.41) and respiratory morbidity (RR 0.68, 95% CI 0.37, 1.25) in first- compared to second-trimester estimations. Female infants estimated in first trimester born ≥41 weeks had lower risk of umbilical artery pH <7.05, NICU admissions and respiratory morbidity; however, CIs were wide. Early ultrasound estimation of gestational age may reduce the excess risk of adverse neonatal outcomes and highlight the role of foetal sex and the timing of ultrasound assessment in the clinical evaluation of preterm and post-term pregnancies.

The impact of placental genomic risk for schizophrenia and birth asphyxia on brain development

The placenta plays a role in fetal brain development, and pregnancy and birth complications can be signs of placental dysfunction. Birth asphyxia is associated with smaller head size and higher risk of developing schizophrenia (SZ), but whether birth asphyxia and placental genomic risk factors associated with SZ are related and how they might impact brain development is unclear. 433 adult patients with SZ and 870 healthy controls were clinically evaluated and underwent brain magnetic resonance imaging. Pregnancy and birth information were obtained from the Medical Birth Registry of Norway. Polygenic risk scores (PRS) from the latest genome-wide association study in SZ were differentiated into placental PRS (PlacPRS) and non-placental PRS. If the interaction between PRSs and birth asphyxia on case-control status was significant, neonatal head circumference (nHC) and adult intracranial volume (ICV) were further evaluated with these variables using multiple regression. PlacPRS in individuals with a history of birth asphyxia was associated with a higher likelihood of being a patient with SZ (t = 2.10, p = 0.018). We found a significant interaction between PlacPRS and birth asphyxia on nHC in the whole sample (t = −2.43, p = 0.008), with higher placental PRS for SZ associated with lower nHC in those with birth asphyxia. This relationship was specific to males (t = −2.71, p = 0.005) and also found with their adult ICV (t = −1.97, p = 0.028). These findings suggest that placental pathophysiology and birth asphyxia may affect early and late trajectories of brain development, particularly in males with a higher vulnerability to SZ. This knowledge might lead to new strategies of treatment and prevention in SZ.

Inter-pregnancy interval and placental weight. A population based follow-up study in Norway

IntroductionWe studied changes in placental weight from the first to the second delivery according to length of the inter-pregnancy interval. MethodsWe followed all women in Norway from their first to their second successive singleton pregnancy during the years 1999–2019, a total of 271 184 women. We used data from the Medical Birth Registry of Norway and studied changes in placental weight (in grams (g)) according to the length of the inter-pregnancy. Adjustments were made for year and maternal age at first delivery, changes in the prevalence of maternal diseases (hypertension and diabetes), and a new father to the second pregnancy. ResultsMean placental weight increased from 655 g at the first delivery to 680 g at the second. The adjusted increase in placental weight was highest at inter-pregnancy intervals <6 months; 38.2 g (95 % CI 33.0g–43.4 g) versus 23.2 g (95 % CI 18.8g–27.7 g) at inter-pregnancy interval 6–17 months. At inter-pregnancy intervals ≥18 months, placental weight remained higher than at the first delivery, but was non-different from inter-pregnancy intervals 6–17 months. Also, after additional adjustment for daily smoking and body mass index in sub-samples, we found the highest increase in placental weight at the shortest inter-pregnancy interval. We estimated no difference in gestational age at delivery or placental to birthweight ratio according to inter-pregnancy interval. DiscussionPlacental weight increased from the first to the second pregnancy, and the increase was most pronounced at short inter-pregnancy intervals. The biological causes and implications of such findings remain to be studied.

Postpartum Lifestyle Behaviors among Women with Hypertensive Disorders of Pregnancy: Data from the HUNT Study.

Hypertensive disorders of pregnancy (HDP) are associated with an increased risk of cardiovascular disease later in life. Clinical guidelines for postpartum follow-up after HDP often recommend lifestyle counseling to reduce this risk. However, knowledge about lifestyle behaviors and perceptions among women with a history of HDP is limited. We linked data from the fourth survey of the population-based Trøndelag Health Study (HUNT4) with data from the Medical Birth Registry of Norway. The associations between HDP and postpartum lifestyle behaviors and perceptions were examined using multivariable logistic regression. In a secondary analysis, HUNT4 participants with a recent history of pre-eclampsia were compared with women with a recent history of pre-eclampsia participating in a postpartum pilot intervention study. Lifestyle behaviors and perceptions were self-reported and included diet (intake frequency of fruits, vegetables, meat, fish, and sugar-sweetened beverages), alcohol intake, physical activity, sleep, smoking, lifestyle satisfaction, and the importance of a healthy lifestyle. Among 7551 parous HUNT4 participants, 610 had a history of HDP. We found no differences in lifestyle behaviors between women with and without a history of HDP. However, women with HDP had higher odds of being unsatisfied with their lifestyle. Women with pre-eclampsia participating in a postpartum lifestyle intervention study tended to have a healthier lifestyle at baseline than women participating in HUNT4. Future studies should explore how lifestyle intervention programs could be adapted to the needs of women who have experienced HDP or other pregnancy complications that are associated with an increased risk of CVD.

The relationship between cesarean delivery and fecundability: a population-based cohort study

BackgroundPrevious studies have found that women with caesarean delivery have fewer pregnancies. Caesarean delivery is also more common among women with lower fecundability. The potential role of caesarean delivery on reduced fecundability is not known. ObjectiveTo assess the bidirectional relationship between caesarean delivery and fecundability. Study DesignThis is a prospective cohort study based on data from the Norwegian Mother, Father, and Child Cohort study linked with the Medical Birth Registry of Norway. We estimated the fecundability ratio (per cycle probability of pregnancy) and relative risk of infertility (time to pregnancy ≥ 12 months) according to mode of delivery in the previous delivery among 42,379 women. For the reverse association, we estimated the relative risk of having a caesarean delivery by fecundability (the number of cycles women needed to conceive) among 74,025 women. ResultsThe proportion of women with infertility was 6.2% (2711/43936) among women with prior vaginal delivery, and 8.6% (518/6036) among women with a prior caesarean delivery, yielding an adjusted relative risk of 1.21 (95% confidence interval: 1.10 to 1.33). Women with previous caesarean delivery also had lower fecundability ratio (0.90, 95% confidence interval 0.88 to 0.93), compared to women with prior vaginal delivery. When assessing the reverse association between fecundability and caesarean delivery, we found that women who did not conceive within 12 or more cycles had higher risk of caesarean delivery (adjusted relative risk 1.55, 95% confidence interval 1.46 to 1.64) compared to women who conceived within the first two cycles. Associations remained after controlling for sociodemographic and clinical risk factors and were observed across parity groups. ConclusionAmong women with more than one child, those who had caesarean delivery had subsequent lower fecundability ratio and increased infertility risk compared to those who had vaginal delivery. However, women who needed longer time to conceive were also more prone to be delivered by caesarean delivery. We therefore found evidence of a bidirectional relationship between caesarean delivery and fecundability. This could be due to a common underlying explanatory mechanism, and the surgical procedure itself may not directly influence fecundability.

Risk of adverse pregnancy outcomes in twin- and singleton-born women: An inter-generational cohort study.

To compare the risk of adverse pregnancy outcomes between twin-born and singleton-born women. We also evaluated whether in utero exposure to pre-eclampsia or preterm delivery affected adverse pregnancy outcomes in women's own pregnancies. Population-based cohort study. Medical Birth Registry of Norway 1967-2020. 9184 twin-born and 492 894 singleton-born women during 1967-2005, with their later pregnancies registered during 1981-2020. Data from an individual's birth were linked to their later pregnancies. We used generalised linear models with log link binomial distribution to obtain exponentiated regression coefficients that estimated relative risks (RRs) with 95% confidence intervals (CIs) for associations between twin- or singleton-born women and later adverse pregnancy outcomes. Pre-eclampsia, preterm delivery or perinatal loss in twin-born compared with singleton-born women. There was no increased risk for adverse outcomes in twin-born compared with singleton-born women: adjusted RRs for pre-eclampsia were 1.00 (95% CI 0.93-1.09), for preterm delivery 0.96 (95% CI 0.90-1.02) and for perinatal loss 1.00 (95% CI 0.84-1.18). Compared with singleton-born women exposed to pre-eclampsia in utero, twin-born women exposed to pre-eclampsia had lower risk of adverse outcomes in their own pregnancies; the aRR for pre-eclampsia was 0.73 (95% CI 0.58-0.91) and for preterm delivery was 0.71 (95% CI 0.56-0.90). Compared with preterm singleton-born women, preterm twin-born women did not differ in terms of risk of pre-eclampsia (aRR 1.05, 95% CI 0.92-1.21) or perinatal loss (aRR 0.99, 95% CI 0.71-1.37) and had reduced risk of preterm delivery (RR 0.83, 95% CI 0.74-0.94). Twin-born women did not differ from singleton-born women in terms of risk of adverse pregnancy outcomes. Twin-born women exposed to pre-eclampsia in utero, had a lower risk of pre-eclampsia and preterm delivery compared with singleton-born women exposed to pre-eclampsia.

Postpartum lifestyle behaviour among women with prior gestational diabetes mellitus: evidence from the HUNT study

IntroductionWomen with a history of gestational diabetes mellitus (GDM) are at increased risk of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD). Recommendations for postpartum follow-up include targeted lifestyle...

Trends in Term Intrapartum Stillbirth in Norway

Fetal death during labor at term is a complication that is rarely studied in high-income countries. There is a need for large population-based studies to examine the rate of term intrapartum stillbirth in high-income countries and the factors associated with its occurrence. To evaluate trends in term intrapartum stillbirth over time and to investigate the association between the trends and term intrapartum stillbirth risk factors from 1999 to 2018 in Norway. This cohort study used data from the Medical Birth Registry of Norway from 1999 to 2018 to examine rates of term intrapartum stillbirth and risk factors associated with this event. A population of 1 021 268 term singleton pregnancies without congenital anomalies or antepartum stillbirths was included in analyses, which were performed from September 2022 to February 2023. The main exposure variable was time, which was divided into four 5-year periods: 1999 to 2003, 2004 to 2008, 2009 to 2013, and 2014 to 2018. The primary study outcome was term intrapartum stillbirth. Risk ratios were calculated, and multivariable logistic regression analyses were conducted to identify factors associated with secular trends of term intrapartum stillbirth. The study population consisted of 1 021 268 term singleton births (maternal mean [SD] age, 29.72 [5.01] years; mean [SD] gestational age, 39.69 [1.27] weeks). During the study period, there were 95 term intrapartum stillbirths (0.09 per 1000 births). Maternal age, the proportion of individuals born in a country other than Norway, and the prevalence of gestational diabetes, labor induction, operative vaginal delivery, and previous cesarean delivery increased over the course of the study period. Conversely, the prevalence of infants large for gestational age, hypertensive disorder in pregnancy, and spontaneous vaginal delivery and the proportion of individuals who smoked decreased. The term intrapartum stillbirth rate decreased by 87% (95% CI, 68%-95%) from 0.15 per 1000 births in 1999 to 2008 to 0.02 per 1000 births in 2014 to 2018. Three in 4 term intrapartum stillbirths (70 of 95) occurred during intrapartum operative deliveries. The increased prevalence of older maternal age and obstetric risk factors were not associated with the variation in intrapartum stillbirth rates among the time periods. The prevalence of term intrapartum stillbirth was higher for individuals who gave birth in maternity units with fewer than 3000 annual births (adjusted odds ratio, 1.67; 95% CI, 1.07-2.61) than for those who gave birth in units with 3000 or more annual births. Findings of this study suggest that, despite increases in maternal and obstetric risk factors, term intrapartum stillbirth rates substantially decreased during the study period. Reasons for this decrease may be due to improvements in intrapartum care.

Paternal and maternal birthweight and offspring risk of macrosomia at term gestations: A nationwide population study.

There is a paucity of data on whether parents' macrosomia (birthweight ≥4500 g) status influences the risk of macrosomia in the offspring. The role of maternal overweight in the generational effect of macrosomia is not known. To estimate the risk of macrosomia by parental birthweight at term and evaluate if this risk varied with maternal body mass index (BMI, kg/m2) early in pregnancy. We used data from the Medical Birth Registry of Norway on all singleton term births (37-42 gestational weeks) during 1967-2017. The primary exposure was parental macrosomia, and the outcome was macrosomia in the second generation. The secondary exposure was maternal BMI. We used binomial regression to calculate relative risk (RR) with a 95% confidence interval. We assessed potential unmeasured confounding and selection bias using a probabilistic bias analysis and performed analyses with and without imputation for variables with missing values. The data included 647,957 singleton parent-offspring trios born at term. The prevalence of macrosomia was 3.2% (n = 41,396) in the parental generation and 4.0% (n = 25,673) in the offspring generation. Macrosomia in parents was associated with an increased risk of macrosomia in offspring, with the RR for both parents were born macrosomic being 6.53 (95% confidence interval [CI] 5.31, 8.05), only mother macrosomic 3.37 (95% CI 3.17, 3.57) and only father macrosomic RR 2.22 (95% CI 2.12, 2.33). These risks increased by maternal BMI in early pregnancy: if both parents were born macrosomic, 17% of infants were macrosomic among mothers with normal BMI. If both parents were macrosomic and the mothers were obese, 31% of offspring were macrosomic. Macrosomia-related adverse outcomes did not differ with parental macrosomia status. Parents' weight at birth and maternal BMI appear to be strongly associated with macrosomia in the offspring delivered at term gestations.

Birthweight of the subsequent singleton pregnancy following a first twin or singleton pregnancy.

Birthweight is an important pregnancy indicator strongly associated with infant, child, and later adult life health. Previous studies have found that second-born babies are, on average, heavier than first-born babies, indicating an independent effect of parity on birthweight. Existing data are mostly based on singleton pregnancies and do not consider higher order pregnancies. We aimed to compare birthweight in singleton pregnancies following a first twin pregnancy relative to a first singleton pregnancy. This was a prospective registry-based cohort study using maternally linked offspring with first and subsequent pregnancies registered in the Medical Birth Registry of Norway between 1967 and 2020. We studied offspring birthweights of 778 975 women, of which 4849 had twins and 774 126 had singletons in their first pregnancy. Associations between twin or singleton status of the first pregnancy and birthweight (grams) in subsequent singleton pregnancies were evaluated by linear regression adjusted for maternal age at first delivery, year of first pregnancy, maternal education, and country of birth. We used plots to visualize the distribution of birthweight in the first and subsequent pregnancies. Mean combined birthweight of first-born twins was more than 1000 g larger than mean birthweight of first-born singletons. When comparing mean birthweight of a subsequent singleton baby following first-born twins with those following first-born singletons, the adjusted difference was just 21 g (95% confidence interval 5-37 g). Birthweights of the subsequent singleton baby were similar for women with a first twin or a first singleton pregnancy. Although first twin pregnancies contribute a greater combined total offspring birthweight including more extensive uterine expansion, this does not explain the general parity effect seen in birthweight. The physiological reasons for increased birthweight with parity remain to be established.

Cerebral palsy in children born after assisted reproductive technology in Norway: Risk, prevalence, and clinical characteristics.

The aim was to investigate the risk, prevalence, and clinical characteristics of cerebral palsy among children born after assisted reproductive technology (ART) in Norway. All liveborn children from 2002 to 2015 were included. Information was collected from the Medical Birth Registry of Norway, linked to the Norwegian Quality and Surveillance Registry for Cerebral Palsy as of December 31, 2022. Logistic regression analyses were used to calculate the prevalence of cerebral palsy per 1000 live births after ART and natural conception with birth year as covariate, crude odds ratios (OR) for cerebral palsy among children born after ART using children born after natural conception as reference, and OR adjusted for potential confounders, with 95% confidence intervals (CI). Potential mediators of the association were studied in stratified analyses. Descriptive statistics were used to compare proportions in clinical characteristics among children with cerebral palsy born after ART and natural conception. Among 833 645 livebirths, 23 645 children were born after ART and of the latter 97 were diagnosed with cerebral palsy. The overall prevalence of cerebral palsy after ART was 4.10 per 1000 live births (95% CI 3.36-5.00), decreasing from 7.79 per 1000 in 2002 to 3.55 in 2015. Compared with children born after natural conception, the OR for cerebral palsy was 2.01 (95% CI 1.63-2.47) adjusted for mother's age at birth, parity, and pre-pregnancy health. When restricted to singletons born at term, the adjusted OR for cerebral palsy was 1.13 (95% CI 0.76-1.69). The distribution of cerebral palsy subtypes and the severity of gross and fine motor function and associated impairments did not differ significantly between children with cerebral palsy born after ART and natural conception. Children born after ART had a risk of cerebral palsy that was twice that of children born after natural conception. The increased risk of cerebral palsy after ART is likely attributed to multiple pregnancies and preterm births. The prevalence of cerebral palsy after ART decreased significantly during the study period, despite an increased use of ART in the population. The distribution of clinical characteristics did not differ between children with cerebral palsy born after ART and those born after a natural conception, suggesting that the risk factors for, and causes of cerebral palsy were similar.

Pregestational maternal risk factors for preterm and term preeclampsia: A population-based cohort study.

Most studies on factors affecting the risk of preeclampsia have not separated preterm from term preeclampsia, and we still know little about whether the predisposing conditions have a differentiated effect on the risk of preterm and term preeclampsia. Our aim was to assess whether diabetes type 1 and 2, chronic kidney disease, asthma, epilepsy, rheumatoid arthritis and chronic hypertension were differentially associated with preterm and term preeclampsia. This is a nationwide, population-based cohort study containing all births registered in the Medical Birth Registry of Norway from 1999 to 2016. Multinomial logistic regression analysis was used to estimate relative risk ratios (RRRs) with 95% confidence intervals (95% CIs), adjusting for maternal age, parity, multiple gestation and all other studied maternal risk factors. We registered 1 044 860 deliveries, of which 9533 (0.9%) women had preterm preeclampsia (<37 weeks) and 26 504 (2.5%) women had term preeclampsia (>37 weeks). Most of the assessed maternal risk factors were associated with increased risk for both preterm and term preeclampsia, with adjusted RRRs ranging from 1.2 to 10.5 (preterm vs no preeclampsia) and 0.9-5.7 (term vs no preeclampsia). Diabetes type 1 and 2 (RRR preterm vs term preeclampsia 2.89, 95% CI 2.46-3.39 and RRR 1.68, 95% CI 1.25-2.25, respectively), chronic kidney disease (RRR 1.55, 95% CI 1.11-2.17) and chronic hypertension (RRR 1.85, 95% CI 1.63-2.10) were more strongly associated with preterm than term preeclampsia in adjusted analyses. For asthma, epilepsy and rheumatoid arthritis, RRRs were closer to one and not significant when comparing risk of preterm and term preeclampsia. Main results were similar when using a diagnosis at <34 weeks to define preterm preeclampsia. Diabetes type 1 and 2, chronic kidney disease and chronic hypertension were more strongly associated with preterm than term preeclampsia.

Childbirth delivery mode and the risk of multiple sclerosis: a prospective population-based study

BackgroundCaesarean section (CS) may affect the risk of developing multiple sclerosis (MS) in the offspring, possibly through changes in gut microbiota composition, but findings from previous studies are inconsistent. We...

Pregnancy complications in last pregnancy and mothers’ long-term cardiovascular mortality: does the relation differ from that of complications in first pregnancy? A population-based study

BackgroundWomen who experience complications in first pregnancy are at increased risk of cardiovascular disease (CVD) later in life. Little corresponding knowledge is available for complications in later pregnancies. Therefore, we assessed complications (preeclampsia, preterm birth, and offspring small for gestational age) in first and last pregnancies and the risk of long-term maternal CVD death, taking women´s complete reproduction into account.Data and methodsWe linked data from the Medical Birth Registry of Norway to the national Cause of Death Registry. We followed women whose first birth took place during 1967–2013, from the date of their last birth until death, or December 31st 2020, whichever occurred first. We analysed risk of CVD death until 69 years of age according to any complications in last pregnancy. Using Cox regression analysis, we adjusted for maternal age at first birth and level of education.ResultsWomen with any complications in their last or first pregnancy were at higher risk of CVD death than mothers with two-lifetime births and no pregnancy complications (reference). For example, the adjusted hazard ratio (aHR) for women with four births and any complications only in the last pregnancy was 2.85 (95% CI, 1.93–4.20). If a complication occurred in the first pregnancy only, the aHR was 1.74 (1.24–2.45). Corresponding hazard ratios for women with two births were 1.82 (CI, 1.59–2.08) and 1.41 (1.26–1.58), respectively.ConclusionsThe risk for CVD death was higher among mothers with complications only in their last pregnancy compared to women with no complications, and also higher compared to mothers with a complication only in their first pregnancy.