Adding to evidence that the flu shot is safe for pregnant women, a new study finds no link between the vaccine and the risk of serious birth defects.
The study, of nearly 9 000 pregnant women who got the flu shot, found that about 2% had a baby with a major birth defect. That was identical to the rate in nearly 77 000 pregnant women who did not get the vaccine. What's more, researchers found, women who got vaccinated were less likely to lose the pregnancy after the 20th week (0.3% vs 0.6%).
Their newborns also had a lower death rate: 0.2% died soon after birth, compared with 0.4% of babies born to unvaccinated moms.
It's not clear if the flu vaccine deserves the credit. But Dr Jeanne S Sheffield, the lead researcher on the work, said it's possible the vaccine helped by preventing severe cases of the flu.
"Can we say for sure that it's the vaccine? No," said Dr Sheffield, from the University of Texas Southwestern Medical Center in Dallas. But, she added, these findings suggest that the flu shot is at least safe, and possibly has a benefit against stillbirth.
Dr Sheffield and her colleagues report the findings in the journal Obstetrics & Gynecology.
Seasonal flu shot
The Centers for Disease Control and Prevention (CDC) and other groups recommend that all pregnant women get a seasonal flu shot.
Still, Dr Sheffield said, many women and doctors alike still have concerns about flu vaccine safety during pregnancy - especially in the first trimester. But in this study, the researchers found that vaccination during the first trimester came with no increased risk of birth defects.
Despite recommendations to get the flu shot, most pregnant women do not. In the U.S., only 10% to 25% of women have been vaccinated each flu season over the last couple decades, Dr Sheffield's team notes.
Based on studies, that seems largely due to safety worries.
On the other hand, Dr Sheffield said "it's amazing" how many women are unaware that the flu itself is considered a risk during pregnancy.
"The flu is a problem in pregnancy," she said. "But we have a vaccine to prevent it. And it's considered safe and effective in any trimester."
A CDC study published last year found "no unusual patterns" of pregnancy complications or newborn health problems among U.S. women who received the flu shot between 1990 and 2009.
Based on cases reported to the CDC's Vaccine Adverse Event Reporting System, the rate of miscarriage was 1.9 per one million vaccinated pregnant women.
(Reuters Health, August 2012)