Overall, Tdap shot safe for mom and baby, study finds

November 13, 2014

IN THE NEWS: California is in the midst of a whooping cough epidemic and infants too young to be vaccinated are most vulnerable to this disease, also known as pertussis. To protect them, the state health department, as well as the Advisory Committee on Immunization Practices and the American College of Obstetricians and Gynecologists recently began recommending that all pregnant women in their third trimester get the Tdap shot, which protects against pertussis, as well as diphtheria and tetanus. KPCC-FM, Southern California Public Radio, asked UC Irvine obstetrician Dr. Jacqueline Guerrero to comment on a new study of the Tdap shot:

But as a new article in the Journal of American Medicine explains, there has been limited data on whether Tdap vaccination during pregnancy affects the health of mothers or their babies… until now.

As part of a JAMA study published this week, researchers analyzed administrative and electronic health record data of more than 123,000 California women -- 21 percent of whom received the Tdap shot during pregnancy between Jan. 1, 2010 and Nov. 15, 2012.
Among their findings:
  • In moms, the Tdap booster shot was not associated with increased risk of preterm birth (before 37 weeks)
  • In babies, the shot was not associated with small-for-gestational births.
  • Also in babies, the shot was not associated with increased risk of hypertension or preeclampsia.
The one finding that raises an eyebrow:
  • Among women who received the shot - at any time during pregnancy - 6.1 percent were diagnosed with chorioamnionitis, slightly more than the 5.5 percent of women who had this condition and didn’t receive the shot. (With chorioamnionitis, bacteria infect the membranes that surround the fetus and the amniotic fluid, and can cause infections for the mother and her fetus.)
  • The researchers note that in the subset of women who were vaccinated during the third trimester - as is recommended - the risk was still increased, but less so.
Jacqueline Guerrero, a professor of obstetrics and gynecology at UC Irvine Medical Center, agreed that this finding - the slightly increased risk for chorioamnionitis - shouldn't be a reason to stop administering Tdap to pregnant women in their third trimester.

"This slightly increased risk of chorioamnionitis is outweighed by the proven benefit of Tdap," she wrote, especially given that pertussis can be deadly for infants.

During this year's epidemic, many California mothers didn't follow these vaccination recommendations. The state knows the vaccination history for 158 – or 48 percent – of whooping cough cases in kids younger than four months old. Of those, 143 moms – or 77 percent – did not receive the Tdap shot during their third trimester.

See the full report at Southern California Public Radio >>

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