Effects of preconceptional paternal drug exposure on birth outcomes: cohort study of 340 000 pregnancies using Norwegian population-based databases.

AIMS: We aimed to explore associations between drugs dispensed to the father prior to conception and pregnancy outcomes, such as pre-term birth, perinatal mortality, foetal growth retardation and birth defects.

METHODS: In this cohort study, two population-based registries, the Medical Birth Registry of Norway and the Norwegian Prescription Database, were linked. The study cohort consisted of 340 000 pregnancies in 2004-10. The association between specific drugs dispensed to the fathers during the last 3 months prior to conception and pregnancy outcomes was explored by estimating odds ratios (ORs) using multivariate logistic regression.

RESULTS: About one quarter (26%) of the fathers were dispensed at least one drug during the last 3 months prior to conception and 1.3% were dispensed at least one drug requiring special attention. Overall, the odds of different adverse pregnancy outcomes were not increased when the father had been dispensed drugs, i.e. the OR and 95% confidence intervals (CIs) for any birth defect when the fathers had been dispensed any drug were 0.99 (0.94, 1.0). When the fathers had been dispensed diazepam we found increased risk of perinatal mortality and growth retardation, with OR and 95% CIs of 2.2 (1.2, 3.9) and 1.4 (1.2, 1.6), respectively.

CONCLUSIONS: Large studies are necessary to reveal increased risk of rare outcomes as specific birth defects. Our study did not indicate that paternal drug exposure is an important risk factor for adverse pregnancy outcomes.