The Nordic countries are Denmark, Finland, Iceland, Norway, and Sweden and comprise a total population of approximately 27 million. The countries provide unique opportunities for joint health registry-based research in large populations with long and complete follow-up, facilitated by shared features, such as the tax-funded and public health care systems, the similar population-based registries, and the personal identity number as unique identifier of all citizens. In this review, we provide an introduction to the health care systems, key registries, and how to navigate the practical and ethical aspects of setting up such studies. For each country, we provide an overview of population statistics and health care expenditures, and describe the operational and administrative organization of the health care system. The Nordic registries provide population-based, routine, and prospective data on individuals lives and health with virtually complete follow-up and exact censoring information. We briefly describe the total population registries, birth registries, patient registries, cancer registries, prescription registries, and causes of death registries with a focus on period of coverage, selected key variables, and potential limitations. Lastly, we discuss some practical and legal perspectives. The potential of joint research is not fully exploited, mainly due to legal and practical difficulties in, for example, cross-border sharing of data. Future tasks include clear and transparent legal pathways and a framework by which practical aspects are facilitated.

The study has no external funding; all costs are covered by ESHRE. There are no competing interests.

IMPORTANCE Maternal antenatal corticosteroid treatment is standard care to accelerate fetal maturation when birth before 34 weeks is imminent. Recently, expansion of the indications beyond 34 gestational weeks has been debated. However, data about long-term outcomes remain limited, especially among infants who after treatment exposure are born at term. OBJECTIVE To study if antenatal corticosteroid treatment is associated with mental and behavioral disorders in children born at term (Ն37 weeks 0 days' gestation) and preterm (<37 weeks 0 days' gestation) and if unmeasured familial confounding explains these associations. DESIGN, SETTING, AND PARTICIPANTSPopulation-based retrospective cohort study using nationwide registries of all singleton live births in Finland surviving until 1 year and a within-sibpair comparison among term siblings. Children were born between

IMPORTANCEWomen with epilepsy frequently need antiseizure medication (ASM) to prevent seizures in pregnancy. Risk of neurodevelopmental disorders after prenatal exposure to AMSs is uncertain.OBJECTIVE To determine whether children exposed prenatally to ASMs in monotherapy and duotherapy have increased risk of neurodevelopmental disorders. DESIGN, SETTING, AND PARTICIPANTSThe Nordic register-based study of antiepileptic drugs in pregnancy (SCAN-AED) is a population-based cohort study using health register and social register data from Denmark, Finland, Iceland, Norway, and Sweden (1996-2017; analysis performed February 2022). From 4 702 774 alive-born children with available mother-child identities and maternal prescription data, this study included 4 494 926 participants. Children from a multiple pregnancy or with chromosomal disorders or uncertain pregnancy length were excluded (n = 207 848).EXPOSURES Prenatal exposure to ASM determined from maternal prescription fills between last menstrual period and birth. MAIN OUTCOMES AND MEASURESWe estimated cumulative incidence at age 8 years in exposed and unexposed children. Cox regression adjusted for potential confounders yielded adjusted hazard ratios (aHRs) with 95% CIs for autism spectrum disorder (ASD), intellectual disability (ID), or any neurodevelopmental disorder (ASD and/or ID).RESULTS A total of 4 494 926 children were included; 2 306 993 (51.3%) were male, and the median (IQR) age at end of follow-up was 8 (4.0-12.1) years. Among 21 634 unexposed children of mothers with epilepsy, 1.5% had a diagnosis of ASD and 0.8% (numerators were not available because of personal data regulations in Denmark) of ID by age 8 years. In same-aged children of mothers with epilepsy exposed to topiramate and valproate monotherapy, 4.3% and 2.7%, respectively, had ASD, and 3.1% and 2.4% had ID. The aHRs for ASD and ID after topiramate exposure were 2.8 (95% CI, 1.4-5.7) and 3.5 (95% CI, 1.4-8.6), respectively, and after valproate exposure were 2.4 (95% CI, 1.7-3.3) and 2.5 (95% CI, 1.7-3.7). The aHRs were elevated with higher ASM doses compared with children from the general population. The duotherapies levetiracetam with carbamazepine and lamotrigine with topiramate were associated with increased risks of neurodevelopmental disorders in children of women with epilepsy: levetiracetam with carbamazepine: 8-year cumulative incidence, 5.7%; aHR, 3.5; 95% CI, 1.5-8.2; lamotrigine with topiramate: 8-year cumulative incidence, 7.5%; aHR, 2.4; 95% CI, 1.1-4.9. No increased risk was associated with levetiracetam with lamotrigine (8-year cumulative incidence, 1.6%; aHR, 0.9; 95% CI, 0.3-2.5). No consistently increased risks were observed for neurodevelopmental disorders after prenatal exposure to monotherapy with lamotrigine, levetiracetam, carbamazepin, oxcarbazepine, gapapentin, pregabalin, clonazepam, or phenobarbital. CONCLUSIONS AND RELEVANCEIn this cohort study, prenatal exposure to topiramate, valproate, and several duotherapies were associated with increased risks of neurodevel...

Maternal PGDM combined with severe maternal obesity markedly increases the risk of several children's psychiatric and mild neurodevelopmental disorders.

ObjectiveTo generate a global reference for caesarean section (CS) rates at health facilities.DesignCross‐sectional study.SettingHealth facilities from 43 countries.Population/SampleThirty eight thousand three hundred and twenty‐four women giving birth from 22 countries for model building and 10 045 875 women giving birth from 43 countries for model testing.MethodsWe hypothesised that mathematical models could determine the relationship between clinical‐obstetric characteristics and CS. These models generated probabilities of CS that could be compared with the observed CS rates. We devised a three‐step approach to generate the global benchmark of CS rates at health facilities: creation of a multi‐country reference population, building mathematical models, and testing these models.Main outcome measuresArea under the ROC curves, diagnostic odds ratio, expected CS rate, observed CS rate.ResultsAccording to the different versions of the model, areas under the ROC curves suggested a good discriminatory capacity of C‐Model, with summary estimates ranging from 0.832 to 0.844. The C‐Model was able to generate expected CS rates adjusted for the case‐mix of the obstetric population. We have also prepared an e‐calculator to facilitate use of C‐Model (www.who.int/reproductivehealth/publications/maternal_perinatal_health/c-model/en/).ConclusionsThis article describes the development of a global reference for CS rates. Based on maternal characteristics, this tool was able to generate an individualised expected CS rate for health facilities or groups of health facilities. With C‐Model, obstetric teams, health system managers, health facilities, health insurance companies, and governments can produce a customised reference CS rate for assessing use (and overuse) of CS.Tweetable abstractThe C‐Model provides a customized benchmark for caesarean section rates in health facilities and systems.

The large variations in severe tears and episiotomies and the negative association between these indicators in 2010 show the importance of improving the assessment and reporting of tears in each country, and evaluating the impact of low episiotomy rates on the perineum.

Background Variations in intervention rates, without subsequent reductions in adverse outcomes, can indicate overuse. We studied variations in and associations between commonly used childbirth interventions and adverse outcomes, adjusted for population characteristics. Methods and findings In this multinational cross-sectional study, existing data on 4,729,307 singleton births at �37 weeks in 2013 from Finland,