Pregnant women who developed 2009 H1N1 influenza were sicker and their infants had worse outcomes, according to data from the 2009 H1N1 influenza pandemic and the 2013-2014 influenza season.
In April 2009, a new influenza A virus, now known as influenza A(H1N1)pdm09, began circulating in California. By June 2011, the World Health Organization had raised the global pandemic level to its highest level, 6. In the 5 years that have passed since then, influenza experts have learned much about how the virus affects pregnant women and their unborn babies.
In a perspective piece published in the October 9 issue of the New England Journal of Medicine, Sonja A. Rasmussen, MD, and Denise J. Jamieson, MD, MPH, both from the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, present current recommendations for vaccinating and treating pregnant women at risk for influenza.
"[B]y implementing the current antiviral treatment recommendations, clinicians can prevent complications in women with influenza," the authors write. "We need to ensure that the information about influenza and pregnancy that has been gained in the 5 years since the 2009 H1N1 pandemic is translated into reductions in the number of illnesses, hospitalizations, and deaths that occur in future influenza seasons."
During the 2013 to 2014 influenza season, when 2009 H1N1 was again the primary circulating influenza virus in the United States, cases of serious illness, hospitalizations, and deaths were reported among young and middle-aged adults and pregnant women.
"Although data were available before the 2009 pandemic suggesting that pregnant women were at increased risk for influenza-associated complications, the pandemic provided solid data on this vulnerability," the authors write. "Pregnant women with 2009 H1N1 influenza were at substantially higher risk for hospitalization than the general population, and they accounted for approximately 5% of deaths from 2009 H1N1 influenza that were reported to the [CDC], even though pregnant women make up only about 1% of the population."
Infants born to mothers who had been severely ill with influenza also were at increased risk for poor outcomes, including preterm birth and small size for gestational age.
Prompt Treatment Critical
Before 2009, pregnant women with influenza were only treated if they had other high-risk medical conditions or severe illness. In 2009, in a significant change in antiviral treatment guidance, the CDC recommended that pregnant women suspected of having 2009 H1N1 influenza "receive prompt antiviral therapy regardless of risk factors, severity of illness, history, or the results of diagnostic testing," the authors write. "During the pandemic, we learned that treating pregnant women with such a medication makes a difference."
"It's very important for physicians' offices to effectively communicate with their patients about what the woman should do if the woman feels that she has influenza-like symptoms. It's very important for her to call her physician's office, rather than show up for a scheduled appointment," James Byrne, MD, chair, Department of Ob-Gyn, Santa Clara Valley Medical Center, San Jose, and affiliated clinical professor, Stanford University School of Medicine, California, told Medscape Medical News.
"She could get more rapid care by actually calling and having a prescription for anti-flu medication ordered for her via telephone," Dr Byrne added. He also noted that by handling such cases over the telephone, clinicians can avoid exposing other pregnant women in their waiting rooms to the virus.
A recent systematic review and meta-analysis that studied the effects of antiviral medications on mortality from 2009 H1N1 influenza among hospitalized pregnant women found that those who were given a neuraminidase inhibitor within the first 2 days after becoming ill were about one fifth as likely to die as those who received treatment later or not at all.
Other studies showed that treatment was still clinically beneficial when started after the first 48 hours of illness. Despite these findings, not all pregnant women with influenza signs and symptoms receive treatment with antiviral drugs, the authors write.
Clinicians should educate their pregnant patients about the need for prompt medical care as well as prevention. However, women should receive antiviral treatment if they develop influenza symptoms, regardless of vaccination status because the vaccine is only about 60% effective.
Vaccination Reduces Risk for Mother, Baby
"Receiving an influenza vaccine reduces the risk of influenza not only for the pregnant woman but also for her infant during the first 6 months of life," the authors write. Research has also shed light on factors that prevent and encourage influenza vaccination of pregnant women.
In September 2014, the American College of Obstetricians and Gynecologists released an updated committee opinion recommending the influenza vaccine for all pregnant women.
"The flu virus is highly infectious and can be particularly dangerous to pregnant women, as it can cause pneumonia, premature labor, and other complications, " Laura Riley, MD, chair of the college's Immunization Expert Work Group, which developed the opinion in conjunction with the college's Committee on Obstetric Practice, said in a news release about the committee opinion. "Vaccination every year, early in the season and regardless of the stage of pregnancy, is the best line of defense."
"Many women are not aware of how dangerous influenza can be when they're pregnant; it's dangerous for both the mother and her child. The influenza vaccine is extremely effective with reducing the risk, but even with the heightened awareness, more than half of pregnant women fail to be vaccinated each year," Dr Byrne explained.
Vaccination coverage increased substantially during the pandemic but has remained at less than 50% since the 2010 to 2011 influenza season.
The authors and Dr Byrne have disclosed no relevant financial relationships.
N Engl J Med. 2014;371:1373-1375. Abstract
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Cite this: Vaccination, Early Flu Treatment Critical for Pregnant Women - Medscape - Oct 09, 2014.
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