Infant outcomes among pregnant women who used oseltamivir for treatment of influenza during the H1N1 epidemic.

OBJECTIVE: This study was undertaken to examine the association between maternal oseltamivir treatment for influenza and infant outcomes during the 2009 HINI influenza pandemic.

STUDY DESIGN: This was a retrospective cohort study using a population-based maternal newborn database including women who gave birth to a singleton infant in the Canadian province of Ontario from November 2009 through April 2010. Risks of small for gestational age (SGA) (10th percentile and 3rd percentile), preterm birth (<37 weeks of gestation), very preterm birth (<32 weeks of gestation), and 5-minute Apgar score <7 associated with maternal exposure to oseltamivir were analyzed by multivariable regression.

RESULTS: A total of 55,355 women with a singleton birth were included in this study. Among them, 1237 (2.2%) women received oseltamivir for treatment or prevention of influenza during pregnancy. Women who took oseltamivir during pregnancy were less likely to have a SGA infant based on the 10th percentile for growth (adjusted risk ratio, 0.77; 95% confidence interval, 0.60-0.98). No association between maternal use of oseltamivir with SGA on 3rd percentile, preterm birth, very preterm birth, and low Apgar score was observed.

CONCLUSION: There is no evidence of an association between maternal use of oseltamivir for influenza and early birth, low Apgar at birth, and poor fetal growth.