Effect of prenatal selective serotonin reuptake inhibitor (SSRI) exposure on birthweight and gestational age: a sibling-controlled cohort study.

Background: Up to 10% of women are exposed to selective serotonin reuptake inhibitors (SSRIs) during pregnancy. Information on their effect on birthweight and gestational age remains conflicting. The aim of this sibling-controlled prospective cohort study is to address shared geneticand family-level confounding to investigate the effects of prenatal SSRI exposure and maternal depression on birthweight and gestational age. Methods: We used the Norwegian Mother and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN). Our study population consisted of 27 756 siblings; 194 were prenatally exposed to SSRIs and 27 500 were unexposed to any antidepressant medication. Random and fixed effects analysis with propensity score adjustment was used to evaluate the effectson birthweight and gestational age. Results: SSRI exposure during two or more trimesters was associated with a decrease in birthweight of 205 g [95% confidence interval (CI) -372 to - 38] and a decrease in gestational length of 4.9 days (95% CI - 9.1 to - 1.4). Neither maternal SSRI use in one trimester, lifetime history of major depression nor depressive symptoms during pregnancy were associated with these pregnancy outcomes (for non-pharmacologically treated depression in two periods in pregnancy, +5 g (95% CI - 56 to + 67) and +4.9 days (95% CI - 4.7 to + 14.7), respectively). Conclusions: Prenatal exposure to SSRIs during two or more trimesters may decrease birthweight and gestational length. Our results indicate that neither maternal depression nor shared genetics and family environment fully explain this association.