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Concerns over Swine Flu H1N1 Vaccine and Pregnancy


Updated November 18, 2009

H1N1 Vaccine and Pregnancy

The CDC strongly recommends swine flu vaccination for all pregnant women. But not everyone is convinced that the H1N1 vaccine and pregnancy are a good match.

Photo © Steve Cole / Getty Images

The 2009 novel H1N1 influenza, better known as swine flu, has been big news from the get-go. Although there are no specific data on H1N1 flu causing miscarriages, healthcare workers believe there may be an increased risk of pregnancy loss for infected moms -- and pregnant women appear to have much higher risk than the general population of suffering severe health complications from swine flu. About 6% of deaths due to swine flu have been among pregnant women, while pregnant women are only 1% of the general population at any given time. Thus, public health agencies such as the CDC are strongly urging pregnant moms to receive H1N1 flu shots to prevent these complications.

Naturally, however, many people have concerns about receiving swine flu vaccinations -- or any flu shots -- during pregnancy. Moms may worry about the safety of thimerosal exposure during pregnancy or that the shots could somehow cause a miscarriage or other harm to the developing baby, and they may be frustrated with the lack of clear data.

Current Status

Because of the known risks swine flu poses to pregnant women, the CDC advises women to receive flu vaccination during any trimester of pregnancy. The CDC's stance on flu vaccination in pregnancy is that there is no evidence that flu vaccinations cause miscarriages, and that it's important not to assume that miscarriages occurring after H1N1 flu vaccination were directly caused by the vaccine simply because of the correlation in timing. Pregnant women are a high-priority group for vaccination and prenatal care providers are being urged to promote the vaccine.


Vaccinations -- in particular shots that contain the preservative thimerosal -- have been receiving a lot of bad press lately due to advocacy groups that are concerned that mercury could cause autism or other developmental problems in children. No studies have proven that thimerosal has any specific health risks, but concerns remain. Plus, this year thimerosal-free versions are available for patients who are not comfortable with thimerosal.

Thimerosal isn't the only issue people are worried about. During pregnancy, expecting moms commonly worry and scrutinize everything they put into their bodies, so even with the reassurances from the CDC, many moms are hesitant about receiving H1N1 vaccination given the lack of data on its safety during pregnancy. In addition, about 15 to 20% of all confirmed pregnancies end in miscarriage, with the majority of miscarriages occurring during the first trimester, so miscarriages are most likely going to occur in pregnant women who have been vaccinated against H1N1 flu, which is an unfortunate coincidence, not a cause and effect. Again, the CDC says there is currently no reason to believe that flu vaccination causes miscarriages, but not everyone is reassured.

Furthermore, other concerns have been raised about swine flu vaccination, ranging from worries over the vaccine being new to not fearing the H1N1 flu virus itself -- and it can be really confusing to sort through all the information out there.

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