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Antenatal flu drugs not linked to newborn risks

Neuraminidase inhibitors in pregnancy not linked to adverse foetal or neonatal outcomes

Louise Prime

Thursday, 02 March 2017

Babies of women who took neuraminidase inhibitors during pregnancy are no more likely to suffer adverse neonatal outcomes or congenital malformations than those whose mothers didn’t, research* published online by the BMJ has confirmed.

During the 2009-10 influenza A/H1N1 pandemic, regulatory agencies in Europe and the US recommended treatment and post-exposure prophylaxis in patients at high risk, including pregnant women, despite limited knowledge on the safety and effectiveness of neuraminidase inhibitors in pregnancy; no randomised controlled trials on their use during pregnancy have been conducted. The two approved neuraminidase inhibitors in Europe are oseltamivir, taken orally, and zanamivir, which is inhaled.

A team of researchers led from the Karolinska Institutet in Stockholm, Sweden, designed a study to evaluate any possible effects exposure to neuraminidase inhibitors during embryo-foetal life on the risk of adverse neonatal outcomes and congenital malformations. They analysed data from national registers on maternal healthcare, births, and prescriptions in Denmark, Norway, and Sweden and the EFEMERIS database from the Haute-Garonne district in France, covering all women together with their singleton infants born at ≥154 days’ gestation between 1 January 2008 and 31 December 2010.

They defined exposed infants as those whose mothers filled a prescription during pregnancy for either of the two neuraminidase inhibitors oseltamivir or zanamivir. Their analysis included 5,824 exposed women and their infants, and 692,232 who were not exposed.

After accounting for possible confounding factors such as maternal age, use of other drugs and smoking, the researchers found that the in utero use of neither oseltamivir nor zanamivir was associated with an increased risk of any of the assessed neonatal outcomes – including low birth weight, low Apgar score, preterm birth, small for gestational age birth, stillbirth, neonatal mortality, and neonatal morbidity. Nor was there an association between increased risk of congenital malformations overall and maternal exposure during the first trimester. When they analysed only the use of oseltamivir, there was again no significantly increased risk of any of the outcomes.

The study authors acknowledged some limitations of their study, such as that they did not assess risks of adverse outcomes before 22 weeks of pregnancy; and some women might have filled their prescription and then not taken the drug.

Nevertheless, they concluded: “We found no increased risk of adverse neonatal outcomes or congenital malformations associated with exposure to neuraminidase inhibitors during pregnancy. Our results support previously reported findings that the use of neuraminidase inhibitors is not associated with increased risks of adverse foetal or neonatal outcomes.”


* Graner S, Svensson T, Beau A-B, et al. Neuraminidase inhibitors during pregnancy and risk of adverse neonatal outcomes and congenital malformations: population based European register study. BMJ 2017; 356: j629. doi: 10.1136/bmj.j629.

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