Tdap During Pregnancy: When It Is Given

The CDC recommends Tdap during pregnancy in the 27th through 36th week of each pregnancy, and it recommends it again in the next one regardless of how recently the last dose was given. The reason is not the pregnant person's own tetanus protection. It is the newborn, who cannot start their own whooping cough series on day one and who is at the greatest risk in exactly those first weeks.

This article covers the timing and the reasoning for Tdap and the seasonal flu vaccine in pregnancy. It does not decide anything for a particular pregnancy — the week, the product and any medical history belong to prenatal care.

When during pregnancy is Tdap given?

Between 27 and 36 weeks. The CDC's page on Tdap vaccination during pregnancy, last reviewed 2 December 2025, recommends that "pregnant women get Tdap during the 27th through 36th week of each pregnancy." The CDC's pregnancy and vaccines page, last reviewed 31 January 2025, gives the same window: "between 27 and 36 weeks of each pregnancy."

That is the third trimester, and it is deliberate. Antibodies produced in response to the vaccine need time to cross the placenta before delivery, which is why a dose in that window is described as optimal rather than a dose at any point in the pregnancy.

If you are already past 36 weeks, or the pregnancy is following a different course, that is a conversation for the prenatal clinician rather than a reason to work it out from a table.

Why is Tdap repeated in every pregnancy?

Because the protection being transferred belongs to that pregnancy, not to the parent's own history. The CDC is explicit on the point: "It doesn't matter when someone got their last tetanus/diphtheria vaccine (Td or Tdap)." A dose two years ago in a previous pregnancy does not stand in for this one.

The mechanism is short-lived by design. The CDC describes it this way: "The antibodies mothers develop in response to these vaccines not only protect them, but also cross the placenta and help protect their babies from serious diseases early in life." Antibodies passed before birth fade over the first months, which is why the timing is measured in weeks of pregnancy rather than years since the last shot.

Tdap and DTaP are the same three diseases in different formulations for different ages; which one goes to whom is the shorter version of that story. The infant's own series does not start at birth — the CDC child and adolescent immunization schedule places the first DTaP dose in the first months of life, which is the gap the maternal dose is meant to cover.

How much protection does it give a newborn?

The CDC publishes two figures for Tdap during pregnancy, both about the youngest infants. The vaccine "prevents more than 3 in 4 cases" of whooping cough in babies younger than 2 months. And vaccination in the third trimester "protected 9 in 10 babies from serious infections that need treatment in a hospital."

Those are the numbers behind the recommendation, and they are the reason the timing question is worth asking at a prenatal visit rather than deferring to the postpartum period. Neither figure is a guarantee for an individual infant, and neither replaces the newborn's own series later in the first year.

Where does the flu vaccine fit?

Alongside it, on the season's clock rather than the pregnancy's. The CDC's vaccines during pregnancy page lists the flu shot and Tdap among the vaccines recommended during pregnancy, and states that the flu shot "can be given before or during pregnancy, depending on whether or not it is flu season during a pregnancy."

On safety, the CDC's wording is direct: "Flu vaccines have been given to millions of pregnant women over the years, and scientific evidence shows that it is safe." The general recommendation on the CDC's flu vaccines page — everyone 6 months and older, every season — is what the household is working from at the same time.

The practical difference between the two is that Tdap has a week number and flu has a month. One is scheduled inside the pregnancy; the other is scheduled inside the season, and the two rarely land on the same visit.

Why does the rest of the household matter?

A newborn meets a lot of people in the first six weeks, and none of the visitors are covered by the pregnancy's doses. Partners, grandparents, older siblings and the cousin who wants to pop by all make their own decisions with their own clinicians. A household flu week is the easiest of those to organise, because it has a calendar rather than a debate.

For grandparents planning a visit, the conversation is better held before the baby shower than in a hospital lobby, and it can stay short: would you check with your clinician about Tdap and flu before you come. You do not need to police anyone's chart. You also do not need to pretend the household is irrelevant. If someone is travelling to meet the baby, add time — appointments and pharmacy stock are not overnight shipping.

What to take to the prenatal visit

Write these down before the appointment, because the room moves quickly:

Which vaccines are recommended for me in this pregnancy, and at which visit?
Where should I read the current CDC language — the pregnancy page, the Vaccine Information Statement for the product, or both?
How will this dose be written on my record so the pediatric office sees it later?
Who in the household should talk to their own clinician before the baby arrives?

Ask for the after-visit note. Pregnancy is exactly when records scatter across a prenatal clinic, a pharmacy flu dose, a hospital and a pediatric office that has never seen you. Vaxnext holds those dated lines per family member on the phone, offline and with no account, so the third-trimester Tdap is still findable in a year.

FAQ

Does a Tdap from a previous pregnancy still count?

No. The CDC recommends Tdap during pregnancy for each pregnancy, in the 27th through 36th week, and states that it does not matter when the last tetanus or diphtheria vaccine was given. The antibodies that cross the placenta are produced in response to that pregnancy's dose, so a dose given two years earlier does not carry over to this newborn.

Is the flu shot safe during pregnancy?

The CDC states that flu vaccines "have been given to millions of pregnant women over the years, and scientific evidence shows that it is safe." The CDC lists the flu shot among the vaccines recommended during pregnancy and notes it can be given before or during pregnancy, depending on the season. Questions about a specific pregnancy belong with the prenatal clinician.

Should partners and grandparents be vaccinated too?

That is their decision with their own clinician, not something a pregnancy can arrange for them. What a household can do is ask early, so that appointment availability is not the reason someone shows up unvaccinated in the first weeks. Keep the request short and factual, and let each adult take it to their own provider.

Not medical advice. This article is general information based on public U.S. CDC pages. It does not replace a clinician. Schedules and country entry rules change — confirm the current official page and your own situation before you act.