Objective: Information on the safety of paternal use of azathioprine (AZA) and 6-mercaptopurine (6-MP) prior to conception is limited. Based on nationwide data from the Danish health registries, we examined the association between paternal use of AZA/6-MP within 3 months before conception and adverse birth outcomes.
Design: This nationwide cohort study is based on data from all singletons born in Denmark from 1 January 1997 through 2013. Children fathered by men who used AZA/6-MP within 3 months before conception constituted the exposed cohort (N=699), and children fathered by men who did not use AZA/6-MP 3 months prior to conception constituted the unexposed cohort (N=1 012 624). The outcomes were congenital abnormalities (CAs), preterm birth and small for gestational age (SGA). We adjusted for multiple covariates and performed a restricted analysis of men with IBD.
Results: There were no significantly increased risks of CAs, preterm birth or SGA in exposed versus unexposed cohorts of children. The adjusted ORs were 0.82 (95% CI 0.53 to 1.28) for CAs, 1.17 (95% CI 0.72 to 1.92) for preterm birth and 1.38 (95% CI 0.76 to 2.51) for SGA. Restricting our analysis to fathers with IBD showed similar results with no significantly increased risk of adverse birth outcomes.
Conclusions: This nationwide study is the largest to date, examining the effect of preconceptual paternal use of AZA/6-MP on birth outcomes in live born singletons. The results of no significantly increased risks of adverse birth outcomes are reassuring and support the continuation of paternal AZA/6-MP treatment during conception.
Keywords: 6-MERCAPTOPURINE; AZATHIOPRINE; EPIDEMIOLOGY; INFLAMMATORY BOWEL DISEASE.
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