Pregnant People Can Pass COVID Antibodies to Baby in the Womb

There’s good news for growing families, as pregnant people can transfer COVID-19 antibodies to their baby in the womb. In a recent study from the American Journal of Obstetrics and Gynecology, researchers looked at pregnant people who tested positive for COVID-19 antibodies.

People studied gave birth between March 22 and May 31, 2020 in New York City, then an epicenter of the pandemic. In 78% of cases, newborns had passive immunity through immunoglobulin G, a type of antibody.

“Transfer of maternal antibodies to the fetus during pregnancy is a highly effective way of protecting the newborn against infections in the first six months of life, a crucial period where their immune system is still developing,” says Elie Hobeika, MD, a board-certified reproductive endocrinologist at Fertility Centers of Illinois.

How Antibodies Transfer to Babies in the Womb

Thanks to the placenta, antibodies can move from parent to baby in the womb. “The placenta has receptors to which circulating antibodies in the maternal blood can attach,” says Hobeika. “Those antibodies are then transported to the growing fetus and provide protection for the first six months of life.”

At the end of the first trimester, antibodies may begin to transfer to the fetus, but the process ramps up as the pregnancy progresses. “Between 28 and 32 weeks of pregnancy, the concentration of circulating antibodies in the fetus reaches 50% of maternal levels, and that increases to equal the maternal levels by 36 weeks, and may exceed those levels at full term,” says Hobeika. 

COVID-19 antibodies are not the first to be passed from parent to baby. For example, doctors give the TdaP vaccine to pregnant people during the third trimester. This protects the infant from tetanus, diphtheria, and pertussis (whooping cough) for the first few months of their life, before they can receive the vaccine themselves, says Sharon Nachman, MD, chief of pediatric infectious diseases and director of the office of clinical trials at Stony Brook Children’s Hospital in New York.

Antibodies also can be transferred from parent to baby during breastfeeding, says Hobeika. 

Transferable Antibodies Can Come From an Infection or the Vaccine

A person can give antibodies to their growing baby regardless of whether the antibodies were generated by an infection or the COVID-19 vaccine. However, how much of the antibodies and for how long can vary immensely between the two.

“The level of antibodies or IgG that you make after a vaccine is much higher than the level of antibody that you make after infection,” says Nachman. “The possibility is if we vaccinate pregnant women, and that vaccine protects them, and the level of protective antibody is very high, then we will also be protecting their infants.”

According to Hobeika, this may lead to increased levels of antibodies in a fetus when the transfer occurs due to a vaccine instead of an infection.

The exact length of time COVID-19 antibodies last post-infection is currently unknown, meaning that parents infected early in their pregnancy may not yet be able to transfer the antibodies to their fetus.

An October 2020 study from Immunology looked at the presence of antibodies in 5,882 people in Pima County, Arizona. Researchers determined that antibodies tended to become undetectable within five to seven months of infection.

In the American Journal of Obstetrics and Gynecology study, symptomatic patients had higher antibody levels than those who had been asymptomatic. People with higher antibody levels were more likely to transfer them to their baby in the womb.

While the COVID-19 vaccine may need to be an annual ritual, research points to its effects lasting for at least a year. “Vaccines typically induce a more pronounced immune response leading to higher levels of circulating antibodies for a longer period of time,” adds Hobeika. 

There has been misinformation circulating that the COVID-19 vaccine is dangerous for people who are pregnant or looking to conceive in the future. There is no evidence that the COVID-19 vaccine poses more risk for pregnant people or interferes with fertility. 

The Increased Risk Pregnant People Face From COVID-19

Pregnant people do face higher risks if they are infected with COVID-19. “In general, pregnant individuals have low immunity at the level of their lungs,” says Hobeika. “While pregnancy does not increase the risk of acquiring COVID-19, it does increase the risk of having a severe infection compared to non-pregnant individuals.

According to Kecia Gaither, MD, double board-certified OB/GYN, maternal fetal medicine specialist, and director of perinatal services at NYC Health + Hospitals/Lincoln, pregnant people with COVID-19 may experience respiratory compromise or arrest, thrombotic phenomena, cardiovascular compromise, elevated liver function tests, preterm birth, or death.

Contact your healthcare professional immediately if you are pregnant and begin to exhibit symptoms of COVID-19 or are exposed to someone who tested positive.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.