Every pregnant woman inevitably faces tough medical decisions, none more divisive than whether to get the tetanus-diphtheria-pertussis (TDaP) vaccine. The TDaP vaccine is available to expectant moms who wish to protect their unborn babies against pertussis, a.k.a. whooping cough, and is administered during the last trimester of pregnancy. Since infants can’t be vaccinated against pertussis before two months of age, that puts newborns at risk during those early weeks of life—unless inoculation occurs while in utero, what’s known as "cocoon immunization." Pertussis is a highly contagious respiratory bacterial disease that can lead to choking, vomiting, seizures and violent coughing that can impede breathing. It’s especially fatal when contracted by infants under one year of age. And yet some believe that the risks of administering the TDaP vaccine to pregnant women—some believe it is linked to complications such as preterm delivery, low birth weight and even preeclampsia—outweigh the potential benefits. But a new study from the HealthPartners Institute for Education and Research in Minneapolis indicates that expectant moms can and should opt for the vaccine without worry. Elyse Kharbanda, lead author of the study, says that, when women receive the vaccine between 27 and 36 weeks’ gestation, they produce antibodies that are then passed on to the child, protecting against the whooping cough bacteria. Kharbanda looked at data involving 123,000 women who gave birth between 2010 and 2012. About one-fifth of those women received the TDaP vaccine during pregnancy, and birth weight didn’t vary dramatically between the vaccinated and unvaccinated. While there was a slightly increased risk of fetal membrane inflammation, or chorioamnionitis, the rates of preterm delivery and preeclampsia were also found to be consistent between both groups. But while there’s evidence showing that there’s little to no risk associated with TDaP cocoon immunization, the benefits haven’t yet been proven, either. Whether the protection is lasting or not remains to be seen, and it’s unknown how women’s increased antibody levels resulting from the TDaP vaccine alter their infants’ immune response to subsequent vaccinations. A Canadian Pediatric Society position statement, published Nov. 3, states that cocoon immunizations “are not cost effective at preventing pertussis deaths” in infants younger than six months. But other countries have taken a pro-TDaP approach: for example, England and the U.S., where the Center for Disease Control (CDC) and Prevention has recommended the TDaP vaccine for all pregnant women since 2011, a position that’s supported by both the American College of Obstetricians and Gynecologists and the American College of Nurse-Midwives. The CDC recommendation came shortly after whooping cough outbreaks occurred in the U.S. Outbreaks simultaneously occurred right here in Canada, in parts of British Columbia, Alberta, southwestern Ontario and New Brunswick. It's no wonder that pregnant moms want some form of protection for their unborn infants. What does all of this mean? If you've been contemplating whether to get the vaccine or not, this study might put your mind at ease. Whatever you decide, talk with your doctor for more about the potential risks and benefits that the TDaP vaccination poses to you and your unborn child, and ensure those who come into direct contact with your infant are vaccinated against pertussis. For more on pregnancy and caring for your infant, check out our bump-to-baby guide. Photo courtesy Tatiana Vdb/FlickrCC