Pregnant women infected with the new H1N1 swine flu have a much higher risk of severe illness and death and should receive prompt treatment with antiviral drugs, U.S. government researchers said on Wednesday.

While pregnant woman have always had a higher risk of severe disease from influenza in general, the new H1N1 virus is taking an exceptionally heavy toll, the researchers said.

“We do see a fourfold increase in hospitalization rates among ill pregnant women compared to the general population,” Dr. Denise Jamieson of the U.S. Centers for Disease Control and Prevention said in a telephone interview.

“We’re also seeing a relatively large proportion of deaths among pregnant women. We report 13 percent in the paper, but that is a very unstable number based on a small number of deaths reported,” said Jamieson, whose study appears in the journal Lancet.

The study was based on the deaths of six pregnant women out of 45 deaths related to H1N1 reported to the CDC between April 15 and June 16.

All of the women were healthy prior to infection, and all developed pneumonia and needed to be put on a ventilator.

Jamieson said 302 deaths have been officially reported to the CDC from the new H1N1 virus.

“Among those, we have relatively complete information on 266 deaths. And of those, 15 have been among pregnant women, which is about 6 percent,” Jamieson said.

Pregnant women make up about 1 percent of the U.S. population, she said, so pregnant women “are definitely over-represented in terms of the proportion of deaths.”

Jamieson said pregnant women who suspect they have influenza should call their doctors promptly. The CDC recommends pregnant women with influenza get antiviral drugs as soon as possible, within the first 48 hours to be most effective.

Dr. Keiji Fukuda of the World Health Organization said WHO has not yet decided on its policy on the use of antivirals for pregnant women with H1N1.

“Given the overall situation in many countries where the supplies of antivirals can be limited at times, to concentrate them on treating people who are sick makes a lot of sense,” he said on Britain’s Sky television.

Fukuda said researchers are debating whether it is best to use antivirals to prevent disease or to treat sick people.

Both the CDC’s Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists recommend that all pregnant women get a seasonal flu shot, but less than 14 percent do, according to the CDC.

The ACIP, which advises the CDC, was meeting on Wednesday to decide who should be first to get the new H1N1 vaccine. Pregnant women are expected to be at the head of the line.

Jamieson said pregnant women need to be aware of the risks if they become ill, but they do not need to change the way they live because of the new H1N1 flu.

“We do not have evidence that pregnant women have increased susceptibility or are more likely to acquire influenza,” Jamieson said.

“It’s just that when they have influenza they are at increased risk of having severe disease,” she said.

By Julie Steenhuysen

CHICAGO (Reuters)