Dose-effect of maternal serotonin reuptake inhibitor use during pregnancy on birth outcomes: A prospective cohort study

Background: While antidepressant use during pregnancy is increasingly common, there is concern about the possible effects of in-utero antidepressant exposure on the child. Our objective was to examine whether there is a dose-effect of maternal serotonin reuptake inhibitors (SRI) during pregnancy on birth outcomes. Methods: Women between 12 and 16 weeks of gestation, who were using an SRI, were eligible for participation in this nation-wide prospective observational cohort study. Recruitment took place between April 2015 and February 2018 (n = 145). SRI exposure and psychopathology symptoms were assessed throughout pregnancy. Exposure was defined as SRI standardized dose at 36 weeks of gestation and mean SRI standardized dose over total pregnancy. Multivariable linear and logistic regression were used to examine the associations with birth weight, gestational age at birth, and being small for gestational age. Results: Maternal SRI dose at 36 weeks of gestation was significantly associated with birth weight (adjusted ß = -180.7, 95%CI -301.1;-60.2, p-value < 0.01) as was mean SRI standardized dose during total pregnancy (adjusted ß = -187.3, 95%CI -322.0;-52.6, p-value < 0.01). No significant associations between maternal SRI dose and gestational age or being small for gestational age were observed. Limitations: Although prospective, we cannot make full causal inferences given that we did not randomize women to different dosages. Conclusion: These findings suggest that careful dosing of SRI use during pregnancy may prevent a negative impact on birth weight and indicate the need for further investigation of causality.