Oseltamivir exposure in pregnancy and the risk of specific birth defects.

Background: Influenza during pregnancy contributes to maternal morbidity and mortality. Neuraminidase inhibitors, including oseltamivir, are recommended for treating women with influenza during pregnancy.

Methods: Data from the Slone Birth Defects Study from 2009 to 2015 were used to investigate associations between oseltamivir and specific birth defects. We classified exposures according to timing in pregnancy and examined 52 and 16 defects with early and potential late pregnancy etiology, respectively; we calculated crude odds ratios (ORs) and 95% confidence intervals (CIs) for defects with three or more exposures.

Results: Among 8,379 cases and 4,190 nonmalformed controls, we identified 79 and 42 oseltamivir exposures, respectively. The majority of defects had no exposures. ORs were elevated for several defects, but the CI excluded the null only for intestinal malrotation (OR: 10.7 [1.8, 45.2]; three exposures).

Conclusions: Largely null findings for specific defects are reassuring. The association with intestinal malrotation, while unstable, warrants further investigation.