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This article was published 10/6/2009 (2633 days ago), so information in it may no longer be current.
TORONTO - There are mounting and troubling signs that swine flu and pregnancy don't mix well.
Six pregnant women in Manitoba are reportedly on ventilators because they are severely ill with the virus. And at least two pregnant women in the United States have died of swine flu complications after delivering babies by C-section.
A pregnant teenager in the Dominican Republic died, as did a pregnant woman in Scotland. A woman in St. Theresa Point, a First Nations community in Manitoba, miscarried after contracting swine flu.
Humankind's relationship with the new swine H1N1 virus is still in its infancy. But people who've studied the issue of pregnancy during flu pandemics don't like the signs they are seeing.
Dr. Denise Jamieson, an obstetrician-gynecologist with the U.S. Centers for Disease Control's division of reproductive health, says she finds the evidence to date "very unsettling."
"I am concerned about this," Jamieson said in an interview from Atlanta.
"There does seem to be increased severity in pregnancy. We don't have hard and fast numbers but there are enough reports that are concerning."
Data released by the CDC last month said at that point, 17 per cent of Americans hospitalized for severe swine flu infections were pregnant women.
A report a couple of weeks back in the World Health Organization's journal, Weekly Epidemiologic Record, noted of 30 swine flu patients hospitalized in California, five were pregnant women. Of those, two developed severe complications - spontaneous abortion and premature rupture of membranes.
Jamieson said the numbers are still small but seem to be pointing to a pattern seen in previous pandemics, when pregnant women were disproportionately harder hit than non-pregnant peers.
Dr. Danuta Skowronski, a flu expert with the British Columbia Centre for Disease Control, recently published a review article on influenza immunization in early pregnancy in the journal Vaccine.
In looking at the evidence about the impact of influenza on pregnancy, she and co-author Dr. Gaston De Serres of Laval University noted that the fatality rate was higher in pregnant women during the 1918 and 1957 pandemics, though not the milder pandemic of 1968.
Skowronski said that given the fact that younger adults don't appear to have antibodies to the new swine flu virus, similar results may be on the cards during a swine flu pandemic.
"If we base it on what we know of the 1918, 1957 pandemics, what we know about pre-existing antibody levels to swine influenza in the population, based on that I would say for this particular virus, pregnant women may suffer more serious consequences, especially in the third trimester," she said.
"And they should probably seek care early if they have influenza-like illness."
Studies done after the disastrous 1918 Spanish flu - which took its heaviest toll on young adults - showed astonishing death rates among pregnant women, said Dr. Michael Osterholm, an infectious diseases expert at the University of Minnesota.
Skowronski's review paper suggests there were also very high rates of spontaneous abortions during that pandemic - 26 per cent in pregnant women who became infected and 52 per cent among those who went on to develop pneumonia from their infection.
Osterholm explained pregnancy is a precarious state for a woman from an immunological point of view. In order that the mother's body does not reject the fetus, part of the immune system has to be effectively dialled down.
Other factors are also believed to come into play, including reduced lung capacity, Jamieson added.
She said that while the CDC doesn't yet have firm numbers, they are hearing that some pregnant women are reluctant to take antiviral drugs when they are diagnosed with swine flu. In some cases, their physicians share the reluctance.
Jamieson said given the risk swine flu poses to pregnant women, any who feel they may have contracted it should seek care quickly and should tell their doctor about potential exposures to people who had the virus. And they should take the antiviral drugs, she said.
"The message we're trying to get out is: 'Don't delay. If you suspect influenza, initiate antiviral therapy appropriately even before you get the testing back," Jamieson said.
"We definitely feel like in a situation like this, the benefits outweigh the risks of giving antiviral medication."
Follow Canadian Press Medical Writer Helen Branswell's flu updates on Twitter at CP-Branswell