This article was originally published on October 11, 2017  and was updated on July 11, 2024.

The whooping cough vaccine protects not only pregnant moms but also their infants, with a study showing that administering the vaccine in the third trimester of pregnancy prevented more than three in four whooping cough cases in babies younger than two months.

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But less than half of pregnant women who delivered between fall 2015 and spring 2016 in the study received the vaccine (called Tdap), according to the Centers for Disease Control and Prevention.

Vaccination during the third trimester was also 90% effective at preventing serious cases of whooping cough, or pertussis, that would otherwise require hospitalization.

"This study reinforces that vaccines during pregnancy protect both moms and their babies, but unfortunately a lot of moms are missing out on this important opportunity," said Michelle Moniz, M.D., M.Sc., an assistant professor of obstetrics and gynecology and a researcher at Michigan Medicine.

"Pregnant women want to do everything they can to help their baby be healthy, and one of the best steps is getting recommended vaccines during pregnancy. Vaccinations help protect pregnant women from illnesses like the flu and help support their baby's immune system, protecting them against life threatening illnesses like whooping cough."

The CDC recommends that women get Tdap during each pregnancy to provide critical short-term protection to babies when they are most at risk of pertussis. 

The study used data from 2011 through 2014 on babies younger than two months from six states, 775 infants total.

More from Moniz in her own words on why immunizations are important during pregnancy.

Protecting mom

Pregnancy changes your immune system. It makes you more likely to get some illnesses and more likely to have severe symptoms. 

Having the flu during pregnancy can cause problems for your pregnancy, including affecting the growth of the baby, causing fetal distress, leading to an early delivery and increasing the chance of a cesarean section. 

Anyone who is pregnant during flu season should get a flu shot as soon as they are available in flu season. Because we don't recommend live vaccines in pregnant women, we only use the flu shot, not the nasal flu mist.

Protecting baby

The amazing thing about vaccinations during pregnancy is that there is evidence that the antibodies your body makes in response to the vaccine are transferred to your unborn child and stay with your baby to provide protection against disease for several months after delivery.

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It's a really powerful way to keep your baby healthy during those early months when his immune system is immature.

Cases of pertussis, or whooping cough, are on the rise. 

Newborn babies are at highest risk of getting it and having severe symptoms. 

Because of this, we recommend that all pregnant women receive the Tdap vaccine during their third trimester of each pregnancy. 

This vaccine protects mom from contracting pertussis if she is not already current on her immunizations. 

But even more importantly, it protects baby from contracting pertussis after birth, because mom's antibodies cross the placenta and protect the baby in the critical few weeks after birth.

That transfer of antibodies to baby is why we strongly recommend the vaccination during each pregnancy, no matter how far apart those pregnancies are. 

Dad, other family members and caregivers should also all be current on their pertussis immunizations since parents and caregivers are the most likely source of pertussis in a newborn.

Addressing concerns

Pregnant women are often very cautious about taking medications or shots during pregnancy, often because they want to avoid anything that might harm the baby. 

It's good to be informed about what's safe for you and your baby during pregnancy. 

When it comes to vaccines, research consistently shows that there's not just an absence of harm in receiving immunizations — there is clear evidence of the benefits.

Both the Tdap and flu vaccines are well-studied and have been proven to be safe and effective in pregnant women and their unborn babies. These shots cannot give you the flu or pertussis. 

There are some rare cases in which vaccinations are not recommended, for example, in women with an egg allergy or those prone to Guillain-Barre syndrome. 

All pregnant women should talk to a prenatal health care provider about vaccines. 

For almost all pregnant women, vaccines are safe, recommended and a great opportunity to protect yourself and your baby.