Concomitant use of antidepressants and benzodiazepines during pregnancy and associated risk of congenital malformations: a population-based cohort study in Taiwan.

Background: Despite the frequent co-administration of antidepressants and benzodiazepines, the association between such concomitant use during pregnancy and the risk of congenital malformations remains inadequately explored. This study aims to examine the association between concomitant use of antidepressants and benzodiazepines during the first trimester and organ-specific congenital malformations.

Methods: We conducted a population-based cohort study using Taiwan's National Birth Certificate Application database, the Maternal and Child Health database, and Taiwan's National Health Insurance database. Pregnant people aged 15-50 years with singleton births between Jan 1, 2004, and Dec 31, 2018, were included. Use of antidepressants and benzodiazepines was defined as at least one prescription during the first trimester, and concomitant use was defined as the overlapping prescription of both drugs with an overlapping prescription period. The primary outcomes were overall congenital malformations and eight organ-specific malformations, consisting of the nervous system, heart, respiratory system, oral cleft, digestive system, urinary system, genital system, and limb malformations. Logistic regression models with propensity score fine stratification weighting approach were used to control for measured confounders. Analyses controlling for confounding by indication and sibling comparison analyses were done to address unmeasured confounders. No individuals with lived experience participated in the research or writing process.

Findings: The cohort included 2 634 021 singleton pregnancies, and 8599 (0·3%) individuals were concomitant users of antidepressants and benzodiazepines during the first trimester (mean age at delivery was 31·8 years [SD 5·2] for pregnancies with exposure to antidepressants and benzodiazepines vs 30·7 years [SD 4·9] for pregnancies without exposure). All study participants were female, and information about ethnicity was not available. Absolute risk of overall malformations was 3·81 per 100 pregnancies with exposure, compared with 2·87 per 100 pregnancies without exposure. The propensity score-weighted odds ratios (weighted ORs) did not suggest an increased risk for overall malformations (weighted OR 1·10, 95% CI 0·94-1·28), heart defects (1·01, 0·83-1·23), or any of the other organ-specific malformations, except for digestive system malformations, for which the weighted OR remained statistically significant after adjustment (1·63, 1·06-2·51). The absence of an increased risk for overall congenital malformations associated with concomitant use of antidepressants and benzodiazepines was supported by the analyses controlling for confounding by indication and sibling-matched comparisons.

Interpretation: The findings of this study suggest that the concomitant use of antidepressants and benzodiazepines during the first trimester is not associated with a substantial increase in risk for most malformation subtypes. However, considering other potential adverse effects of using both medications concomitantly, a thorough assessment of the risks and benefits is crucial for clinical decision making.

Funding: National Science and Technology Council.