WEDNESDAY, Jan. 16, 2013 (HealthDay News) -- Pregnant women were urged to get a flu shot during the 2009 H1N1 pandemic, and new evidence supports that advice.
Norwegian researchers have found that vaccination in pregnancy was safe for mother and child, and that fetal deaths were more common among unvaccinated moms-to-be.
Influenza is a serious threat to a pregnant woman and her unborn child, said Dr. Camilla Stoltenberg, director general of the Norwegian Institute of Public Health in Oslo, lead researcher of the new study.
"Our study indicates that influenza during pregnancy was a risk factor for stillbirth during the pandemic in 2009," she said. "We find no indication that pandemic vaccination in the second or third trimester increased the risk of stillbirth."
With this year's flu pummeling many people across the United States, experts say the best way a pregnant woman can protect her unborn baby from flu complications is by getting a flu shot.
"In addition to protecting the mother against severe influenza, the vaccine protects the fetus and the child in the first months after birth, when the child is too young to be vaccinated," Stoltenberg said.
The U.S. Centers for Disease Control and Prevention recommends a flu shot for everyone over 6 months of age. Besides pregnant women, the CDC says the elderly and anyone with a chronic condition such as asthma or diabetes are especially vulnerable to infection.
For the study, published Jan. 16 in the New England Journal of Medicine, Stoltenberg's team collected data on more than 117,000 women in Norway who were pregnant between 2009 and 2010 -- the time of the H1N1 pandemic. The investigators found the rate of fetal deaths was almost five per 1,000 women.
During the pandemic, 54 percent of the women were vaccinated during their second and third trimester, which greatly reduced their risk of contracting the flu, the study authors noted.
For women who did get the flu, the risk of fetal death increased dramatically, the researchers found. Among vaccinated women, the risk of fetal death was far less, they added. Fetal death was defined as any recorded miscarriage or stillbirth after the first trimester.
Moreover, the vaccine was safe, wasn't linked to fetal deaths, and may have reduced the risk of fetal death, Stoltenberg said.
Experts weren't surprised by the results.
"This study confirms what we already know, that pregnancy is a dangerous time for the flu, and H1N1 was particularly problematic for pregnant women," said Dr. Marc Siegel, an associate professor of medicine at NYU Langone Medical Center in New York City.
The flu is especially risky for pregnant women because the virus can pass through the placental barrier and infect the fetus, Siegel explained.
This can result in fetal death or developmental problems, including mental development, he added.
"It's crucial for pregnant women to get a flu shot," Siegel said. "It's important to educate women, and this study helps," he added, noting some women may need convincing because they've been told to avoid certain medications during pregnancy.
Another expert, Dr. Loralei Thornburg, assistant professor of obstetrics and gynecology at the University of Rochester in Rochester, N.Y., said the body's response to infection changes during pregnancy.
"It's kind of an immunosuppressant," she said. "So when you get a bad virus in pregnancy, your body doesn't have the same ability to respond. Preventing infection in pregnancy is really the key."
The bottom line: "Every woman should get the flu vaccine," Thornburg said.
For more information on flu and pregnancy, visit Flu.gov.