When is it recommended to administer Tdap during pregnancy?

Administering the Tdap vaccine between 27 and 36 weeks of gestation is recommended because this timing optimizes the maternal antibody response and the transfer of antibodies to the fetus. Vaccination during this window helps protect both the mother and newborn from pertussis (whooping cough), which can be particularly severe in young infants.

The immune system is more responsive at this stage of gestation, increasing the likelihood of the mother developing a strong immune response that can transfer protective antibodies through the placenta. These antibodies help provide the baby with some level of immunity against pertussis until they can be vaccinated after birth.

In contrast, administering Tdap before 27 weeks may not allow sufficient time for maternal antibody levels to rise, and vaccination after 36 weeks could risk lower antibody transfer to the fetus, as the pregnancy is nearing term. While it is possible to administer the vaccine at any time during pregnancy, the most effective and protective timing is specifically within the recommended window.