Swine Flu Hits Pregnant Women Harder

New study shows higher death rate and higher rate of hospitalizations, making a case for vaccination.

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As a government panel decides today who should be among the first to get the swine flu vaccine, many experts are calling for pregnant women to step to the front of the line. That's because new research shows pregnant women who get swine flu are more likely to develop severe complications that result in hospitalization or even death, according to a study published today in the journal Lancet.

"We hope that pregnant women are placed in the high-priority group for vaccinations because our research shows that they're disproportionately represented among the deaths" in this country caused by the H1N1 virus, says study leader Denise Jamieson, an obstetrician-gynecologist in the division of reproductive health at the Centers for Disease Control and Prevention in Atlanta. Of the 45 deaths from swine flu reported in the study, which collected data from April to May, six were pregnant women; that group represented 13 percent of the deaths. That's far higher than expected, since pregnant women make up only 1 percent of the population. What's more, those women who died were young and healthy and had low-risk pregnancies.

Jamieson adds that since the data were collected, there have been 302 swine deaths in the U.S. population, and 15 were pregnant women, representing 6 percent of the deaths. Though that is a lower percentage, the numbers still suggest that pregnant women are more prone to dangerous infections. The exact reasons for the increased susceptibility aren't known, but Jamieson says it could involve the decreased lung capacity that occurs during pregnancy, which makes it easier for the virus to multiply in the lungs. Or it could be because pregnancy weakens certain components of the immune system. (It strengthens others.)

There were certain similarities among the pregnant women who died. They all developed pneumonia and went into acute respiratory distress. None of them were treated with antiviral drugs like Tamiflu within the first 48 hours after they developed symptoms; in fact, by the time they were treated they had been sick for at least six days and as long as 15 days. "All pregnant women who died did not receive antivirals soon enough to benefit their treatment," the CDC said in a prepared statement that accompanied the study. The agency now recommends that pregnant women who have flu symptoms should immediately be treated with the drugs, preferably in the first two days, to lower the severity and duration of the infection.

Jamieson says she'd like to see more diagnostic flu tests performed by OB-GYNs on pregnant women who develop fevers, sore throats, and other possible flu symptoms. "There's limited access to these tests right now, but I do think more emphasis needs to be put on testing pregnant women" to ensure that they're treated promptly and properly, she explains. She also says that doctors need to do a better job of getting pregnant women vaccinated against the flu since seasonal flu is also associated with more severe complications—like heart and lung problems—during pregnancy. Fewer than 15 percent of pregnant women get a regular flu vaccine, even though the CDC started recommending it in 2004.

What about concerns over the mercury preservative thimerosal, which is present in most flu vaccines? (Pregnant women are told to avoid foods high in mercury because of its potentially detrimental effects on a fetus's brain.) "It does seem reasonable that doctors should stock and provide a thimerosal-free vaccine to their pregnant patients," says Jamieson. Such vaccines are currently available for seasonal flu and will also be available for the H1N1 vaccine. Frequent hand washing is another good precaution pregnant women can take, but Jamieson says there's no reason to avoid crowded places or public transportation, as the British government has recommended.

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