What Do We Know about the COVID-19 Vaccines and Pregnancy?

Two vaccines to prevent COVID-19 illness are now available in the United States, but since pregnant women were not enrolled in the vaccine trials, how should they determine if vaccination is right for them?

"One of the most common questions I've received from our staff and patients is whether the COVID-19 vaccines are safe for women of reproductive age—including those who are pregnant, breastfeeding, or thinking about becoming pregnant," says Mary D'Alton, MD, chair of the Department of Obstetrics and Gynecology at Columbia University Vagelos College of Physicians and Surgeons and director of services for the Sloane Hospital for Women at NewYork-Presbyterian/Columbia University Irving Medical Center.

D'Alton and experts in maternal-fetal medicine and fertility from Columbia and NewYork-Presbyterian recently addressed these questions in town halls for faculty, staff, and students to discuss what is known about the safety of these vaccines for women of reproductive age.

Do pregnant women face greater health risks from COVID-19?

Based on a recent CDC report on symptomatic COVID-19 in more than 400,000 women of reproductive age, the CDC now includes pregnant women in its higher-risk category for COVID-19 illness. 

The study—the largest to date—found that pregnant women with COVID-19 were three times more likely to be admitted to the ICU, nearly three times as likely to require mechanical ventilation, and nearly twice as likely to die compared with non-pregnant women. The risk is even higher in pregnant women with underlying health conditions such as obesity, diabetes, and heart disease and for certain racial and ethnic groups. (For example, while 14% of women in the study were Black, they accounted for more than a quarter of deaths among pregnant women.)

"While the absolute risk for women is low, it's important to have this in mind when we advise women who are pregnant or planning a pregnancy about whether to get vaccinated," says Dena Goffman, MD, professor of obstetrics and gynecology at Columbia University Vagelos College of Physicians and Surgeons and chief of obstetrics at NewYork-Presbyterian/Columbia University Irving Medical Center. 

Are the new vaccines safe for women who are pregnant or breastfeeding?

Although the vaccine trials did not enroll pregnant women, between 30 and 40 participants became pregnant during the course of the trials, which included over 70,000 participants.

"This exclusion is not new or different," says Cynthia Gyamfi-Bannerman, MD, professor of women's health at Columbia University Vagelos College of Physicians and Surgeons and a maternal-fetal medicine specialist at NewYork-Presbyterian/Columbia University Irving Medical Center. "In fact, for many interventions that are studied outside of pregnancy, pregnant women tend to be excluded."

Gyamfi-Bannerman adds, "Even though the number of women who became pregnant during the trials was very small, there were no differences in outcomes compared with non-pregnant women in either the vaccine or placebo groups."

In the town halls, the experts said that it is highly unlikely the components of the vaccine would cross the placenta, suggesting it should be safe for pregnant women. Breastfeeding women also were not included in the trials but the benefits of vaccination likely outweigh any small theoretical risks of vaccination for those who are breastfeeding.

Unlike vaccines that contain live or weakened viruses to trigger an immune response, the new vaccines deliver mRNA, which contains instructions for making a harmless protein found on the surface of the coronavirus. The immune system recognizes the protein as foreign and begins producing antibodies to destroy it. The mRNA is rapidly degraded and eliminated within two to three days.

The manufacturers also submitted data to the FDA from animal studies, which showed that the vaccines had no adverse effects on female reproduction, embryo development, or postnatal development.

Clinical trials are now getting underway to study the safety and efficacy of these vaccines in approximately 2,400 pregnant women, and NewYork-Presbyterian/Columbia University Irving Medical Center expects to begin enrolling patients in late winter. In the meantime, the CDC has launched a safety monitoring program to capture data on pregnant women who have been vaccinated.

"I think it's important for us to encourage pregnant individuals to participate in these trials," says Gyamfi-Bannerman. "In the meantime, we will share the data we have on vaccination in our pregnant patients with the CDC as part of its safety monitoring program."

When should pregnant women get vaccinated?

According to Goffman, pregnant women should consider getting vaccinated as soon as they are eligible. "Some women and their physicians may be worried about vaccination during the first trimester, but based on what we know about how these vaccines work and increased COVID-19 risks during pregnancy, we are very comfortable with first-trimester vaccination," she says.

Goffman counsels pregnant patients based on their own specific risks of COVID-19 exposure, as well as risk factors for severe illness with COVID-19. Risk factors that should be considered include age over 35, comorbid conditions such as obesity and other medical problems, being from a racial or ethnic minority group, and living in a community with higher COVID-19 rates. 

Pregnant women who plan to be vaccinated should get vaccinated as soon as possible, especially if they have a high-risk pregnancy, Goffman says. Vaccination is also recommended for eligible patients who have had COVID-19 and currently have antibodies, as long as they are no longer infectious.

Is there any truth to fears that the vaccines could cause infertility and miscarriage?

Some have theorized that similarities between one of the virus's proteins and a protein required for placental development could mean that antibodies generated by the vaccine would also attack the placenta.

"There is no evidence that the Pfizer or Moderna vaccines cause infertility," says Zev Williams, MD, PhD, chief of the division of reproductive endocrinology and infertility at NewYork-Presbyterian/Columbia University Irving Medical Center. "Contrary to a lot of misinformation on social media, there is no significant similarity between the target of the vaccines and surface proteins on the placenta. If there was cross-reactivity between the vaccine and the surface of the placenta, you would also expect to see an increase in miscarriage among pregnant women with COVID-19, because people infected with the actual virus produce the same antibodies.  But we haven't seen that happen," says Williams, who also notes that analyses of both proteins found they are actually significantly different.

To date, roughly 25 million Americans have been infected with SARS-CoV-2, but there hasn't been an uptick in pregnancy loss or congenital anomalies, the experts said in the town halls.

"Unfortunately, both miscarriage and COVID-19 are very common, so it's easy to understand why people would try to link the two conditions," Williams says. 

"When it comes to infertility, there are no obvious symptoms, so it's understandable that people are fearful that something they are doing—taking certain medications, living in certain environments, or engaging in certain behaviors—could affect fertility," adds Williams.

"The preponderance of evidence suggests that potential risks associated with vaccination are low, though the risk of complications from COVID-19 during pregnancy is high. We recommend that women who are planning to undergo fertility treatment get vaccinated as soon as they are eligible."

My partner has COVID-19—can the virus be transmitted via sex?

An initial study looking at whether SARS-CoV-2 may be transmissible via sex found no evidence of the virus in semen from men who had recovered from COVID-19, but research is still ongoing.

"We have a disease that has been shown to have a bigger impact on men, and we can't say definitively that the virus that causes this disease isn't transmissible via sex," says Joseph Alukal, MD, associate professor of urology at Columbia University Vagelos College of Physicians and Surgeons and a urologist at NewYork-Presbyterian/Columbia University Irving Medical Center. "When my male patients ask me if they—or their brothers and fathers—should get the vaccine, my answer is uniformly yes."