Page ContentT-dap ImmunizationFirst Trimester | Second Trimester | Third Trimester | Postpartum T-dap vaccination during pregnancy is critical for the prevention of pertussis in newborns until they're old enough to be vaccinated. The American College of Obstetrics and Gynecologists (ACOG) website shares answers to commonly asked questions about the T-dap vaccine:What is pertussis?Pertussis (also called whooping cough) is a highly contagious disease that causes severe coughing and difficulty breathing. People with pertussis may make a "whooping" sound when they try to breathe and gasp for air. Pertussis can affect people of all ages and can be serious, even deadly, for babies less than a year old. In recent outbreaks, babies younger than 3 months have had the highest risk of severe disease and of dying from pertussis.What is T-dap?The tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine is used to prevent three infections: tetanusdiphtheriapertussisI'm pregnant. Should I get a T-dap shot? Yes. All pregnant women should get a T-dap shot in the third trimester, preferably between 27 weeks and 36 weeks of gestation. The Tdap shot is a safe and effective way to protect you and your baby from serious illness and complications of pertussis.When should I get the T-dap shot? Experts recommend that you get the Tdap shot during the third trimester (preferably between 27 weeks and 36 weeks) of every pregnancy. The shot will help you make protective antibodies against pertussis. These antibodies are passed to your fetus and protect your baby until he or she begins to get vaccines against pertussis at 2 months of age. Receiving the shot early in the 27 to 36-weeks-of-gestation window is best because it maximizes the antibodies present at birth and will provide the most protection to the newborn.