Nervous system drugs taken by future fathers and birth defects in offspring: a prospective registry-based cohort study

OBJECTIVES: To evaluate the association of paternal intake of antipsychotics, anxiolytics, hypnotics and sedatives, antidepressants, selective serotonin reuptake inhibitors (SSRIs) and (benzo)diazepines during the development of fertilising sperm with birth defects in offspring. DESIGN: Prospective registry-based cohort study. SETTING: Total Danish birth cohort 1997–2016 using Danish national registries. PARTICIPANTS: All 1 201 119 Danish liveborn singletons born 1997–2016 were eligible, 39 803 (3.3%) of whom had at least one major birth defect. EXPOSURE: Offspring were considered exposed if their father had filled at least one prescription in the relevant drug category during development of fertilising sperm (the 3 months prior to conception). PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome was the diagnosis, in the first year of life, of at least one major birth defect as categorised in the EUROCAT guidelines. Secondary outcome was the diagnosis, in the first year of life, of at least one major birth defect in any of the EUROCAT subcategories. Adjusted ORs (AORs) were calculated, along with their 95% CIs, adjusted for year, education, smoking status and age of the mother, and education, disposable income and age of the father. RESULTS: This study found weak or null associations between birth defects and selected drugs. Specifically, antidepressants (17 827 exposed births) gave 3.5% birth defects (AOR 0.97 (0.89 to 1.05)). Diazepines, oxazepines, thiazepines and oxepines (as antipsychotics, 1633 offspring) gave 4.7% birth defects (AOR 1.22 (0.97 to 1.54)), attenuated to 1.13 when excluding by mothers’ prescriptions. The study was well powered assuming 100% therapy adherence, while assuming 50% therapy adherence, the study remained well powered for the largest groups (SSRIs and antidepressants overall). CONCLUSIONS: Antipsychotics, anxiolytics, hypnotics and sedatives, antidepressants, SSRIs and benzodiazepine-derived anxiolytics, when taken by the father during development of fertilising sperm, are generally safe with regard to birth defects.