Editor’s note: This article originally ran December 3, 2021, and was updated January 10, 2022, to reflect updated public health guidance.
Pregnancy is all about timing: when you ovulate, when you conceive, your first, second and third trimesters, your due date.
So when should pregnant women or women trying to conceive receive their COVID-19 booster shots? As soon as possible, says Brian Brimmage, MD, an OB-GYN who delivers babies at UNC Rex Hospital.
That means whether you’re 6 weeks pregnant, 35 weeks pregnant or hope to be pregnant soon, get a booster shot as soon as you’re eligible.
If you weren’t vaccinated for COVID-19 and now you’re pregnant, it’s especially important that you get the shot right away.
“We want to protect mothers as effectively as we can, because we know the risk of being intubated or dying of COVID in pregnant women (as opposed to their non-pregnant peers) is significantly higher,” Dr. Brimmage says. “Obviously, a pregnant woman getting seriously ill with COVID is dangerous for her and her baby.”
Risks to Pregnant Women
Pregnant women are at increased risk for severe illness from COVID-19, and those who contract the virus during pregnancy also face a higher risk of preterm birth and stillbirth. Unvaccinated pregnant women are especially at risk. Since vaccines became widely available, the overwhelming majority of people hospitalized with COVID-19 have been unvaccinated.
Vaccination of pregnant women has lagged because of some moms’ concerns about receiving the vaccine, but there’s been no evidence that the vaccine causes any harm to the mother or baby, Dr. Brimmage says. That’s why the CDC and the leading groups for obstetricians and gynecologists recommend the vaccine for pregnant people.
“There is zero evidence whatsoever that the vaccine or booster causes miscarriage, stillbirth or any type of infertility,” Dr. Brimmage says. “We do know it can be lifesaving for pregnant women, and we don’t yet know if there are long-term effects of a pregnant woman having COVID-19 on her developing baby that the vaccine can prevent.”
Building Antibodies for Moms and Babies
COVID-19 booster shots are now available to people who received their last dose five months ago, for Pfizer and Moderna, or two months ago, for Johnson & Johnson.
Evidence shows that the vaccines work well over the long term in preventing severe disease, but there are some signs that protection wanes after several months.
Vaccines prompt the body’s immune system to make antibodies to the coronavirus that can spring into action when you encounter the virus. Pregnant women who are vaccinated make antibodies that cross the placenta, enter the baby’s bloodstream and offer some protection to the baby after birth. That’s why, for example, pregnant women receive the Tdap vaccine, typically early in the third trimester, to later protect their vulnerable newborns from whooping cough.
That vaccine is given late in the pregnancy to maximize antibody production, because it’s entirely for the benefit of the baby, Dr. Brimmage says. Whooping cough in adults tends to be mild, and most women will have been vaccinated as children.
The COVID-19 vaccine, on the other hand, protects mom and baby, so the timing considerations differ. Yes, it’s possible that getting the COVID-19 vaccine later in pregnancy, such as during the third trimester, could result in more antibodies in the baby’s bloodstream, but no one knows that for sure, Dr. Brimmage says. The research is ongoing.
What is known for sure is that infection at any point in pregnancy can be harmful to the mother and potentially the baby, which is why Dr. Brimmage recommends vaccination and booster shots as soon as possible.
“We know the increase in risk for pregnant women is high,” he says. “That maternal risk scares me more than the possibility of not perfectly optimizing the amount of antibodies crossing to the baby.”
No Link Between Vaccines and Infertility
For people trying to conceive now, in a few months or in the years to come, here’s something not to worry about: There’s no evidence the COVID-19 vaccines cause any sort of infertility whatsoever, Dr. Brimmage says.
“That theory has taken hold online, but based on all of the evidence so far, there’s nothing there,” he says.
And what if you’re trying to get pregnant and want to wait for a booster in the hopes of passing antibodies to your baby? That’s not the best choice, Dr. Brimmage says, because it can take several months to get pregnant, and in the meantime, COVID-19 is still a real threat.
Choosing the Best COVID-19 Booster Shot
Health officials are advising people who received the Pfizer or Moderna mRNA vaccines to get boosted with either shot. They’re also recommending that people who initially received the single-dose Johnson & Johnson vaccine consider boosting with one of the mRNA shots to increase protection.
Unfortunately, there’s not clear data yet on the best approach for pregnant women when it comes to sticking with your shot or mixing and matching, says Dr. Brimmage, who himself took Pfizer for his initial doses and Moderna for his booster.
“I can’t say definitively whether it’s better to stick with your type or get a different booster,” he says, “but I am confident that it’s the right choice to get your booster shot as soon as it’s available to you, especially if you’re pregnant.”
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