H1N1 and Pregnancy: What Do We Know?

The 2009 H1N1 pandemic caused anxiety and concern, especially for pregnant women and their physicians. The Centers for Disease Control (CDC) recognized this special patient population and the increased risk for serious problems and negative outcomes-both for the women and their unborn babies. As such, the CDC advised doctors to provide antiviral medicines to those with symptoms of the flu and vaccines to those pregnant women who were eligible. They further partnered with the American College of Obstetricians and Gynecology, the American Medical Association, and the American Academy of Family Physicians to educate clinicians and urge their participation in the 2009 H1N1 vaccination programs.

Now that the crisis is behind us, research is emerging that details the real risks of the illness as well as the vaccines and treatments. So what do the data show?

Dr Katherine A. Poehling, associate professor of pediatrics and epidemiology and prevention at Wake Forest University School of Medicine, Winston-Salem, North Carolina, and colleagues conducted a surveillance study to determine if maternal vaccination during pregnancy conferred protection later on to the infants. Their work is published online in the American Journal of Obstetrics & Gynecology.

The researchers studied 1510 hospitalized infants younger than 6 months who were hospitalized with fever and/or respiratory symptoms anytime from November to April during the 2002–2009 influenza seasons. Laboratory-confirmed influenza was found in approximately 10% (151) of the infants. Nineteen percent (294) of the mothers reported that they had received the influenza vaccine during their pregnancy. Poehling and colleagues found that 12% (18) of the mothers with infants who had influenza-positive results had been vaccinated; 20% (276) of the mothers whose infants did not test positive for influenza had received flu vaccine during pregnancy.

“Infants of vaccinated mothers were 45%–48% less likely to have influenza hospitalizations than infants of unvaccinated mothers,” the researchers reported. “Our results support the current influenza vaccination recommendation for pregnant women.”

Meanwhile, Dr Hector Mendez-Figuero, fellow of maternal fetal medicine in the department of obstetrics and gynecology at the Alpert Medical School of Brown University, Providence, RI, and colleagues sought to gain a better understanding of the health and well being of infants born during the 2009 H1N1 influenza pandemic.

Their prospective study included 41 pregnant women with influenza-like illness. Approximately 39% of the women were found to have 2009 H1N1 infection. Both the women with H1N1 and those with influenza-like illness had similar rates of live births and an average gestational length of 39 weeks. Apgar scores and cord gas pH values were also similar for both groups of women. The researchers did find, however, a difference in birth weights. On average, infants with mothers who had H1N1 weighed 3186 g; infants born to women with influenza-like illness had an average weight of 3471 g at birth-285 g more than the average in the H1N1 group.

More Information

• CDC H1N1 Resources for Obstetric Health Care Providers
• NEJM: H1N1 Influenza Center Archive

Related Content

• Seeking Infertility Services? Experts Recommend Seeking H1N1 Immunization First
• Educational Tutorial:H1N1 Virus Infection and Pregnancy

References

• Poehling KA, Szilagyi PG, Staat MA et al. Impact of maternal immunization on influenza hospitalizations in infants.  Am J Obstet Gynecol. February 24, 2011.
• Mendez-Figueroa H, Raker C, Anderson BL. Neonatal characteristics and outcomes of pregnancies complicated by influenza infection during the 2009 pandemic. Am J Obstet Gynecol. February 28, 2011.