American Board of Internal Medicine (ABIM) Certification Practice Exam

At what stage of pregnancy should all women receive the Tdap vaccine?

1. First trimester

2. Second trimester

3. 27-36 weeks

4. Upon delivery

The correct answer is: 27-36 weeks

The Tdap vaccine is recommended during pregnancy to protect both the mother and the newborn from pertussis (whooping cough). The optimal time for administering the Tdap vaccine is between 27 and 36 weeks of gestation, specifically during the third trimester. This timing allows for the best transfer of maternal antibodies to the fetus, enhancing the newborn's protection against pertussis during the first few months of life, when they are most vulnerable. Vaccination during this window also helps ensure that the mother has enough time to develop antibodies, which can be passed to the baby in utero before birth. Administering the vaccine earlier than 27 weeks may not provide the same level of immunity to the newborn, while giving it too late (after 36 weeks) may not allow sufficient time for optimal antibody transfer. Therefore, the recommended window is specifically to maximize the health and safety of both mother and child.