A new study based on more than 117,000 pregnancies in Norway has found that there was no risk of still-births for pregnant women who took vaccine against 2009 H1N1 influenza virus. However, there was a significant increase in the number of still-births in women who didn't get vaccinated and were infected with influenza.

"Pregnant women should find it reassuring that we found no harmful effects on the fetus associated with H1N1 vaccination," Siri Haberg, M.D., Ph.D., of the NIPH, first author of the study said in a press release.

The study was conducted by researchers from the U.S. National Institutes of Health and the Norwegian Institute of Public Health (NIPH). Although, healthcare providers had urged women to get flu shots during the H1N1 influenza pandemic 2009-2010, media reports of women having pregnancy complication post vaccination discouraged some women to get the flu-shots.

The data for the study came from registries and medical records from Norway. Researchers found that there were more than 117,347 eligible pregnancies in Norway between 2009 and 2010. The data was then combined with records of doctor visits, birth records, and vaccination registries. They found that pregnancy loss for women who had influenza infection was two times higher than in women who didn't get the infection. No such increase of fetal loss was seen in pregnant women who had received vaccination.

"Most important is that vaccinations protect pregnant women against influenza illness, which could be harmful for both the mother and the baby. If pregnant women are worried about their fetus, then getting a flu shot is a good thing to do," Allen Wilcox, M.D., researcher from the National Institute of Environmental Health Sciences (NIEHS) and co-author of the study.

According to Centers for Disease Control and Prevention, vaccination against influenza does not just keep women and their fetuses healthy, but also protects the baby after birth.

The study is published in the New England Journal of Medicine.