Joanna is a 28-year-old woman, currently 20 weeks pregnant with her second pregnancy. Her first pregnancy ended in a miscarriage at 10 weeks. She presents for a routine prenatal care visit. Joanna has no history of chronic illnesses or allergies, and her current pregnancy has been uncomplicated so far. During the visit, Joanna is counseled about the importance of vaccinations during pregnancy. The Tdap vaccine is discussed as essential between 27 and 36 weeks of gestation. Why is the Tdap vaccine specifically administered between 27-36 weeks of pregnancy?
