Bridging the gap between obstetrics/gynecology and psychiatry with population-based cohorts to understand mental health risk factors

Linked pregnancy and birth registers bridge obstetrics and psychiatry by connecting perinatal exposures with mental health outcomes across the life course. This lecture reviews Nordic cohort studies combining population analyses with discordant-sibling or sister comparisons. These designs control genetic and environmental factors shared within families, but pregnancy-specific confounding and measurement error can remain.

Across published studies, prematurity and impaired fetal growth show the most consistent associations with later neurodevelopmental and psychiatric outcomes, although patterns differ by diagnosis. Among 3.44 million singleton births, associations of very preterm birth and low five-minute Apgar score with stress-related disorders attenuated in sibling analyses, whereas a small association with caesarean delivery persisted.

Unpublished analyses extend this framework to reproductive and transdiagnostic phenotypes. In 2.14 million offspring, neonatal compromise was more strongly associated with externalizing than internalizing disorders within families. Sister-comparison analyses showed different early-life profiles for premenstrual disorders and peripartum depression despite hypothesized shared sensitivity to reproductive hormonal change.

Perinatal exposures may represent causal influences, markers of familial vulnerability, or both. Combining population and family designs can identify developmental signals for mechanistic studies integrating symptoms, biospecimens, omics, and neurobiology.