AbstractBackground and aimPaternal use of analgesics during the time of conception and adverse birth outcomes are poorly studied. We investigated the association between paternal exposure to non‐steroid anti‐inflammatory drugs and opioids within 3 months before the date of conception and the risk of adverse birth outcomes (preterm birth, small for gestational age, low Apgar score, and major congenital malformations).MethodsWe used nationwide data from the Danish health registers. We included information on all singleton live births, and their fathers and mothers from 1997 to 2018. We created two exposed cohorts, children with preconception paternal exposure to (1) non‐steroid anti‐inflammatory drugs and (2) opioids. The unexposed cohort was children without preconception paternal exposure to non‐steroid anti‐inflammatory drugs or opioids, and we performed a sub‐analysis against paternal use of acetaminophen (paracetamol). We used logistic regression models to estimate the odds ratios of adverse birth outcomes including 95% confidence intervals.ResultsWe identified 1,260,934 children, 45,667 children with paternal exposure to non‐steroid anti‐inflammatory drugs, 10,086 children with paternal exposure to opioids, and 1,205,181 unexposed children. The adjusted odds ratio for preterm birth was 1.08 (95% confidence interval, 1.03–1.13) after paternal exposure to non‐steroid anti‐inflammatory drugs and 1.21 (95% confidence interval, 1.08–1.35) after paternal exposure to opioids. The adjusted odds ratio for small for gestational age was 1.09 (95% confidence interval, 1.03–1.17) after paternal exposure to non‐steroid anti‐inflammatory drugs, and 1.03 (95% confidence interval, 0.88–1.21) after paternal exposure to opioids. We found null‐associations for a low Apgar score and major congenital malformations. Estimates were attenuated when compared against paternal paracetamol exposure.ConclusionsOverall, we found null‐associations across the comparisons made. Weak associations were found for paternal exposure to non‐steroid anti‐inflammatory drugs or opioids and preterm birth and small for gestational age, but not with low Apgar score or major congenital malformation. All associations were attenuated when compared against an active comparator of paternal paracetamol exposure. The effect sizes were small and less likely to be of clinical relevance.