(HealthDay News) – Pandemic influenza A (H1N1) infection in pregnancy is associated with an increased risk of fetal death, and vaccination is associated with a non-significant reduction in the risk of fetal death, according to a study published online Jan. 16 in the New England Journal of Medicine.

Siri E. Håberg, MD, from the Norwegian Institute of Public Health in Oslo, and colleagues linked Norwegian national registries and medical consultation data to explore the safety of influenza vaccination of pregnant women among 117,347 eligible pregnancies in Norway from 2009–2010.

Within the sample, fetal mortality was 4.9 deaths per 1,000 births. During the 2009 influenza pandemic, the researchers found that 54% of pregnant women were vaccinated in their second or third trimester. The risk of an influenza diagnosis was significantly reduced with vaccination during pregnancy (adjusted hazard ratio [aHR], 0.3). The risk of fetal death was significantly increased among pregnant women with a clinical diagnosis of influenza (aHR, 1.91). Vaccination during pregnancy correlated with a non-significant reduction in the risk of fetal death (aHR, 0.88; 95% confidence interval, 0.66–1.17).

“Given the danger posed by maternal influenza virus infection for fetal survival, our study adds to growing evidence that vaccination of pregnant women during an influenza pandemic does not harm – and may benefit – the fetus,” the authors write.

Full Text