First author Dr. Siri Haberg of the Norwegian Institute of Public Health and colleagues initiated the study to help address the question of vaccine safety, by taking advantage of Norway's registries and medical records system following the H1N1 influenza pandemic between spring 2009 and fall 2010.
Haberg spent one year of her postdoctoral fellowship in the National Institute of Environmental Health Sciences Epidemiology Branch -- part of the National Institute of Health.
Study co-author Dr. Allen Wilcox of the National Institute of Environmental Health Sciences Epidemiology and colleagues combined data from obstetrical visits, birth records and vaccination registries to investigate whether the influenza vaccination posed a risk to pregnancy.
The study, published in the New England Journal of Medicine, found influenza infection increased the risk of fetal loss by up to two-fold, but influenza vaccination did not increase the risk of loss. Instead, the results suggest that vaccination reduces the risk of fetal loss, the study said.
"Most important is that vaccinations protect pregnant women against influenza illness, which could be harmful for both the mother and the baby," Wilcox said in a statement. "If pregnant women are worried about their fetus, then getting a flu shot is a good thing to do."