The corresponding delivery figures in 2016 taken from the MBRN
were 4,003 vaginal births and 839 caesarean sections.
The source population eligible for inclusion in the present study (n = 74,774) were women participating in MoBa who had responded to questionnaire 1 and questionnaire 2 and were registered in MBRN with a singleton delivery, including stillbirths.
Information about hypospadias and cryptorchidism was retrieved from MBRN. MBRN includes all live births and stillbirths with a gestational age > 16 weeks.
Information about singleton or plural delivery, infant sex, maternal age at delivery, paternal age, infant birth weight, gestational age, in vitro fertilization (IVF), and previous stillbirths was retrieved from the MBRN. Gestational age was calculated from expected date of delivery on the basis of first-trimester ultrasound.
The prevalence of hypospadias in our study is similar to the prevalence in MBRN (0.2%) in mothers not exposed to anti-epileptic drugs (Veiby et al.
Birth weight was measured by the midwife who attended the birth and reported to MBRN (Irgens 2000).
Parity was classified based on data from both MoBa and MBRN and categorized as primiparous or multiparous.
For the present analysis we considered as potentially eligible all women with baseline questionnaire and MBRN data for the first pregnancy in which they were enrolled in MoBa [n - 85,910).
Women classified by the MBRN with unspecified diabetes before or during pregnancy were excluded from the analysis of T2DM and GDiM.
The latter analysis was conducted among the subset of women born in 1967 (when the MBRN was established) or later, with available birth weight (88% of 70,539).
Excluding women with nonconfirmed hypertension [reported only in the baseline questionnaire or MBRN (n = 351)] did not materially change the association with hypertension, so they were included in the analyses.
Among women with a diagnosis of GDM in the MBRN, 88.3% were validated against the pregnancy medical records; and among those without a diagnosis of GDM in the MBRN record, none was classified with GDM by the medical records.