Birth outcomes among women exposed to neuraminidase inhibitors during pregnancy


Helle Kieler, MD, PhD, Centre for Pharmacoepidemiology, Karolinska Institutet, Building T2, Karolinska University Hospital, SE 171 76 Stockholm, Sweden. E-mail:



To compare birth outcomes between women exposed and unexposed to the antiviral medications oseltamivir or zanamivir during pregnancy.


This was an observational cohort study including women who gave birth to singletons in Sweden 2005–2007 and their infants. We obtained information from the national health registers and evaluated risks of low Apgar score, small for gestational age (SGA), low birth weight, preterm delivery, congenital malformations, birth-related death (stillbirth and neonatal death combined), and neonatal morbidity by conditional logistic regression. The unexposed [n = 860] were matched to the exposed [n = 86] by birth year and fetal gender.


A total of 81 women filled a prescription with oseltamivir only, 2 with zanamivir, and 3 with both oseltamivir and zanamivir. Compared with the unexposed infants, the exposed ones had higher risks of late transient hypoglycemia (crude OR = 4.00, 95%CI: 1.26–12.76). There were no statistical increased risks of low Apgar score, congenital malformations, SGA, low birth weight, preterm birth, or birth-related death. Adjusting for maternal age, parity, smoking, and body mass index had minor effects on the results. None of the women exposed to oseltamivir or zanamivir had been admitted to hospital for influenza during their pregnancy.


Except for an increased risk of late transient hypoglycemia, we found no increased risks of adverse birth outcomes among infants exposed to neuraminidase inhibitors in fetal life compared with the unexposed. Copyright © 2011 John Wiley & Sons, Ltd.