American Board of Internal Medicine (ABIM) Certification Practice Exam

For pregnant women, what is the recommended timing for the Tdap vaccine?

1. First trimester only

2. Second trimester only

3. Third trimester only

4. Between 27 and 36 weeks of gestation

The correct answer is: Between 27 and 36 weeks of gestation

The recommended timing for administering the Tdap (tetanus, diphtheria, and pertussis) vaccine during pregnancy is between 27 and 36 weeks of gestation. This timeframe is critical because vaccination during this period maximizes the maternal antibody response and, consequently, the transfer of protective antibodies to the fetus. Administering the vaccine in the third trimester has been shown to enhance the neonate's immunity to whooping cough, which can be severe in infants. Vaccinating after 27 weeks ensures that the maternal immune system has had adequate time to produce antibodies that will then be passed on to the baby before birth. This timing also aligns with the recommendations from health organizations, which emphasize the importance of maternal vaccination in reducing the incidence of pertussis in young infants, who are most vulnerable in the early months of life. Other options, such as only administering the vaccine in the first, second, or only the third trimester, do not allow for the optimal maternal antibody response or the best transfer of protective antibodies to the fetus, thereby increasing the potential risk of pertussis in newborns. Thus, the correct timing is clearly established as between 27 and 36 weeks of gestation, making this answer the most appropriate choice