No increased risks to newborns linked to taking influenza drugs during pregnancy

This is the largest study to date to assess potential risks of taking antiviral drugs (known as neuraminidase inhibitors) during pregnancy and the results support previous findings.

Seasonal influenza occurs every year and millions of pregnant women risk severe illness during seasons with a more aggressive strain.

Regulatory agencies in Europe and the USA therefore recommend neuraminidase inhibitors for pregnant women with confirmed or suspected influenza, or those exposed to close contacts with the illness, despite limited knowledge on their safety and effectiveness during pregnancy.

So a team of researchers based in Scandinavia and France decided to assess risks of adverse birth outcomes in association with neuraminidase inhibitors during pregnancy.

The study involved almost 6,000 women who were prescribed any of the two neuraminidase inhibitors, oseltamivir or zanamivir, during pregnancy -- and almost 700,000 women who did not receive prescriptions during a pregnancy in the same period (2008 to 2010).

After several health-related factors were taken into account, such as age, smoking and use of other medications, the team found no increased risks of adverse outcomes including low birth weight, low Apgar score (a test of a baby's condition at birth), preterm birth, stillbirth, or birth defects.

The findings remained the same when the analyses were restricted to oseltamivir exposure only.

The researchers point out that their study included some limitations that could have influenced the findings. For example, the study did not assess risks of adverse outcomes before 22 weeks of pregnancy, and some women could have filled a prescription without taking the drug

However, they say their results "support previously reported findings that the use of neuraminidase inhibitors is not associated with increased risks of adverse fetal or neonatal outcomes."