The Tdap vaccine is recommended between 27 and 36 weeks of every pregnancy because this timing gives your body enough time to produce protective antibodies and transfer them to your baby through the placenta before birth. Tdap protects against three diseases: tetanus, diphtheria and pertussis, commonly known as whooping cough. Pertussis poses the greatest risk to newborns, and babies cannot receive their own pertussis vaccine until 2 months of age. That gap leaves newborns vulnerable during their first weeks of life. According to the CDC, receiving the Tdap vaccine during the third trimester prevents 78% of pertussis cases in babies younger than 2 months. This guide explains what the Tdap shot does, why your OBGYN recommends it during each pregnancy, and how the timing of your vaccination directly affects the level of protection your newborn receives at birth.
What Is the Tdap Vaccine and What Does It Protect Against?
Tdap stands for tetanus toxoid, reduced diphtheria toxoid and acellular pertussis. The Tdap vaccine protects against three bacterial diseases:
- Tetanus is caused by bacteria that can enter the body through a wound. The infection produces a toxin that causes muscle stiffness, jaw locking and difficulty breathing.
- Diphtheria is a bacterial infection that affects the throat and airways. It can cause a thick coating in the back of the throat that makes breathing and swallowing difficult.
- Pertussis (whooping cough) is a highly contagious respiratory infection that causes severe, uncontrollable coughing fits. Pertussis is the primary reason the Tdap shot is recommended during pregnancy. Newborns with whooping cough face risks including hospitalization, pneumonia, seizures and in rare cases, death.
The Tdap vaccine is an inactivated vaccine. It does not contain live virus or bacteria and cannot cause the diseases it protects against. The adult Tdap shot is a booster to the DTaP series children receive in infancy. Vaccination during pregnancy is a proven way to protect your baby during the first weeks of life, when their immune system is not yet able to mount its own defense against pertussis.
Why Is the Tdap Vaccine Recommended During Every Pregnancy?
The American College of Obstetricians and Gynecologists (ACOG) and the CDC recommend the Tdap vaccine during each pregnancy, regardless of when you last received a tetanus booster or a prior Tdap shot. Antibody levels decrease over time, and each new pregnancy requires a fresh dose to produce the highest possible antibody concentration for transfer to the fetus.
The process works in a straightforward sequence. After you receive the Tdap shot, your immune system produces antibodies against pertussis. Those antibodies cross the placenta and enter your baby’s bloodstream during the third trimester. Your baby is born with a supply of protective antibodies that lasts until they begin their own DTaP vaccine series at 2 months of age. This transfer of maternal antibodies is called passive immunity, and it is the only way to protect your newborn against pertussis during those first vulnerable weeks.
Your OBGYN can administer the Tdap vaccine alongside other prenatal vaccines during the same visit. ACOG confirms that Tdap, the flu shot and the COVID-19 vaccine can all be given safely at the same prenatal appointment. Scheduling them together reduces the number of additional visits needed during your third trimester.
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Why Does Timing Matter for Tdap During Pregnancy?
The recommended window for the Tdap vaccine in pregnancy is 27 to 36 weeks gestation. Getting the shot as early in that window as possible produces the best results.
Your immune system takes approximately 2 weeks to develop a full antibody response after vaccination. Once those antibodies are circulating in your blood, they begin transferring to the fetus. The earlier you receive the vaccine within the 27-to-36-week window, the more time your body has to build and transfer antibodies before delivery.
| Timing | What Happens | Impact on Newborn Protection |
| Week 27-28 (earliest recommended) | Antibodies develop within ~2 weeks; 10-12 weeks of transfer time before full-term delivery | Maximum antibody concentration at birth |
| Week 32-34 (mid-window) | Antibodies develop; 6-8 weeks of transfer time | Good protection, slightly lower antibody levels than earlier vaccination |
| Week 36 (end of window) | Antibodies develop; minimal transfer time before delivery | Some protection, but less antibody transfer than earlier vaccination |
| After delivery (postpartum) | Mother develops antibodies; no placental transfer occurs | Baby does not receive passive immunity; mother reduces her own risk of transmitting pertussis |
Many OBGYN practices align the Tdap shot with the glucose screening visit or Rh immunoglobulin administration, both of which typically happen around 27-28 weeks. This approach keeps your prenatal visit schedule efficient while giving your baby the strongest start. You can read more about how your prenatal appointments are structured in our guide on how many ultrasounds you will have during pregnancy.
Is the Tdap Vaccine Safe During Pregnancy?
Yes. Both FDA-approved Tdap vaccines (Boostrix and Adacel) are approved for use during pregnancy. As noted, Tdap is not a live vaccine, which is one reason it has a strong safety profile during pregnancy.
The CDC monitors vaccine safety through the Vaccine Adverse Event Reporting System (VAERS). No safety signals have been identified for babies whose mothers received Tdap during pregnancy. ACOG’s updated February 2026 guidance on maternal immunizations reaffirms that no evidence of adverse fetal effects exists from inactivated vaccines, bacterial vaccines or toxoids administered during pregnancy. The safety profile of Tdap during pregnancy has been studied extensively across multiple large-scale evaluations. You can learn more about the evidence supporting vaccinations during pregnancy from Dr. Iloabuchi’s feature on WSB-TV.
Common side effects are mild and temporary:
- Soreness or swelling at the injection site (upper arm)
- Low-grade fever
- Fatigue or body aches
- Headache
These side effects typically resolve within 1 to 2 days. Severe reactions to the Tdap vaccine are extremely rare in adults. The benefits of protecting your newborn against pertussis far outweigh the brief discomfort of the vaccine.
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How Can Family Members Help Protect Your Newborn?
Getting the Tdap vaccine during pregnancy is the most effective step for protecting your baby against whooping cough. The second step is making sure the people around your baby are vaccinated too.
This strategy is called cocooning. Partners, grandparents, siblings and other caregivers who have not received a Tdap vaccine should get one at least 2 weeks before meeting the baby. That 2-week window allows their immune systems to build antibodies before they have close contact with the newborn. Newborns can catch pertussis from anyone in close proximity. Older siblings and grandparents are common sources of transmission.
The CDC notes that cocooning alone is not a sufficient substitute for maternal vaccination. Postpartum Tdap administration protects the mother but does not provide passive immunity to the baby. Maternal vaccination during pregnancy remains the primary strategy for newborn protection, and cocooning adds an extra layer of defense around the baby before the baby’s own vaccine series begins. You can read more about keeping your baby safe from infections in our overview of prenatal infection prevention.
Get Your Tdap Vaccine at Gwinnett OB/GYN in Snellville, GA
The Tdap vaccine during pregnancy gives your newborn a head start on protection against whooping cough during the weeks before they can receive their own vaccines. Timing your shot early in the 27-to-36-week window maximizes the antibodies your baby receives at birth.
The board-certified OBGYN team at Gwinnett OB/GYN brings over 45 years of experience in prenatal care. The practice administers Tdap and flu vaccines in-office as part of routine prenatal appointments. Your provider discusses the recommended vaccination timing at your visits and can administer the Tdap shot during a scheduled appointment without requiring an additional trip. All deliveries take place at Eastside Medical Center.
Gwinnett OB/GYN serves patients in Snellville and surrounding communities, including Lawrenceville, Duluth, Loganville, Stone Mountain, Norcross and Lilburn. Schedule your prenatal appointment at Gwinnett OB/GYN to discuss your vaccination plan and give your baby the strongest protection from day one.