The Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis) vaccine was approved for use in 2005. It was only administered to caregivers and parents after a child is born because it was believed to cause whooping cough transmission.
This all changed in 2010 when whooping cough outbreaks caused a spike in infant deaths, prompting California to recommend the vaccine as routine for pregnant women.
Since then, the Tdap vaccine has been recommended by the Advisory Committee on Immunization for administration to women between 27 and 36 weeks of pregnancy.
There was little data to begin with that showed Tdap adversely affected the health of mothers and children during pregnancy, but now a study has cleared up the association, noting the vaccine is not responsible for preterm deliveries or lower-than-usual birth weight in infants.
HealthPartners Institute for Education and Research's Elyse Kharbanda, M.D., M.P.H. and colleagues analyzed administrative healthcare databases from two California Vaccine Safety Datalink sites to determine whether administering Tdap during pregnancy increased risks of adverse effects during pregnancy or birth.
The sites provided access to data on 123,494 pregnancies ending in live birth from Jan. 1, 2010, to Nov. 15, 2012. Out of this number, 21 percent or 26,229 women were given Tdap while they were pregnant.
According to the researchers, out of all the pregnancies included in the study, 8.4 percent of those given Tdap vaccinations and 8.3 of those who weren't led to births where infants had low birth weight. For those on Tdap, 6.3 percent had preterm deliveries while non-Tdap pregnancies that ended in premature births were 7.8 percent.
For pregnancy-related health concerns, the study showed that receiving a Tdap vaccine is not connected to increased risks of hypertensive disorders.
For chorioamnionitis, or the inflammation of membrane surrounding the fetus, 6.1 percent of those on Tdap were diagnosed with the condition while only 5.5 percent of those not given Tdap developed it. Chorioamnionitis is the only instance that the Tdap vaccine increased risks but the researchers note for cautious interpretation since the risk generated was small.
The study "Evaluation of the Association of Maternal Pertussis Vaccination With Obstetric Events and Birth Outcomes" was published in the Journal of the American Medical Association. Other authors include Gabriela Vazquez-Benitez, PhD; Nicola Klein, M.D., PhD; Heather Lipkind, M.D., M.S.; Craig Cheetham, PharmD, M.S.; Saad Omer, PhD; Allison Naleway, PhD; Simon Hambidge, M.D., PhD; Michael Jackson, PhD; Grace Lee, M.D., M.P.H.; Natalie McCarthy, M.P.H.; James Nordin, M.D., MPH; and Frank DeStefano, M.D., M.P.H.
