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Are COVID-19 vaccines safe for pregnant women?

February 23, 2021 | Valerie Elwell
Pregnant woman gets vaccinated.
“Given the abundance of data, I strongly believe that pregnancy should be considered a high-risk health condition for COVID-19 vaccine priority,” says Dr. Carol A. Major, a UCI School of Medicine professor of obstetrics and gynecology who directs maternal-fetal services for UCI Health. 

With COVID-19 vaccinations now underway in the United States, women who are pregnant, nursing or thinking of conceiving are asking if the vaccines are safe for them and their babies, given that they risk severe complications if they contract the virus.

Offering a definitive answer isn’t easy because doctors lack data, says UCI Health obstetrician Dr. Carol A. Major, director of maternal-fetal services at UCI Medical Center, which was recently named a top U.S. maternity hospital for safety and quality.

Pregnant and nursing women were excluded from clinical trials of the Pfizer-BioNTech and Moderna vaccines, which have been authorized by the U.S. Food and Drug Administration (FDA) for emergency use.

It is routine to exclude pregnant and nursing women from most vaccine trials because they’re considered a “vulnerable population.” This historical exclusion of pregnant women from clinical trials was intended to protect them and the developing fetus from the potential harms of new procedures or medicines.

Now, however, Pfizer has begun its highly anticipated clinical trial to evaluate the vaccine in pregnancy. They plan to enroll approximately 4,000 healthy pregnant women over the age of 18, from North America, South America, Europe and Africa.  

COVID-19 and pregnancy

Pregnant women are at increased risk for serious illness and death from COVID-19 compared to nonpregnant women, studies show. While the absolute risk of death among pregnant women with COVID-19 remains low at 1.5 per 1,000 women, the risk is 70% higher in pregnant women than in nonpregnant women.

The Centers for Disease Control and Prevention (CDC) recently assessed the impact of the SARS-CoV-2 virus among more than 400,000 COVID-19-positive women between ages 15 and 44 — 23,434 of whom were pregnant and were experiencing symptoms.

After adjusting for age, race, ethnicity and underlying conditions — such as diabetes, cardiovascular disease and chronic lung disease — pregnant women were three times more likely to be admitted to an intensive care unit (ICU), and 2.9 times more likely to need mechanical ventilation assistance to breathe compared to nonpregnant women of the same age group.

Outcomes for pregnant women ages 35 to 44 were even worse; these women were four times more likely to require mechanical ventilation and two times more likely to die than nonpregnant women of that age group.

A recent study from Washington state found that pregnant women were infected with COVID-19 at a 70% higher rate than non-pregnant women of similar ages. Additionally, the rates of infections in women of color were far higher than expected.

“For these reasons, pregnant women might want to make a personal choice to receive the vaccine, especially if they work in frontline jobs,” says Major, a professor of obstetrics and gynecology in the UCI School of Medicine. “Given the abundance of data, I strongly believe that pregnancy should be considered a high-risk health condition for COVID-19 vaccine priority.”

'No red flags'

Dr. Anthony Fauci, the nation’s leading infectious disease expert and director of the National Institute of Allergies and Infectious Diseases (NIAID), said in a Feb. 3 interview with the Journal of the American Medical Association (JAMA) that “there have been ‘no red flags’ seen in more than 10,000 pregnant women who have recently received COVID-19 vaccine shots so far.”

He added that the FDA would continue to monitor them over time.

The (CDC), the American College of Obstetricians and Gynecologists (ACOG) and the Society for Maternal-Fetal Medicine recommend offering the new mRNA vaccines to pregnant and breastfeeding women who are eligible for vaccination, but advises patients to first consult their doctor.

The World Health Organization (WHO) also says pregnant women at high risk of exposure to SARS-CoV-2 (e.g., healthcare workers) or who have comorbidities that add to their risk of severe disease, may be vaccinated — in consultation with their healthcare provider.

Weighing vaccination

“Those who are pregnant, nursing or trying to become pregnant, should consider several factors when deciding whether to get the vaccine,” says Major, a leading expert in high-risk pregnancies. These include:

  • Assessing your risk for becoming infected with COVID-19 based on the number of cases in your community and your level of interaction with family, friends and others.
  • Concerns for any potential vaccine effects on a developing fetus are usually focused on the first trimester when organs are forming. Vaccinations for influenza and Tdap (tetanus, diphtheria and pertussis) are encouraged in the later stages of pregnancy with no ill effects.
  • The Pfizer and Moderna vaccines use messenger RNA (mRNA) to build immunity to the virus. The vaccine stays in the inoculated arm, where it builds antibodies to the virus and then is flushed from the body. This type of vaccine cannot cross the placental barrier and reach the fetus. However, the antibodies your body creates do pass to through the placental barrier and breastmilk to protect your baby.
  • While the Pfizer and Moderna trial results have no data yet to indicate a safety recommendation for such women, 36 women trial participants became pregnant and are continuing to be monitored for any effects. And more than 10,000 U.S. women who are pregnant have been vaccinated with no reported ill effects. 

Major says it's important to discuss your concerns and desires with your doctor, as well as the best timing if you choose to get the two-dose vaccine series.

Vaccines and high-risk pregnancy

Doctors use the term “high risk” to describe a pregnancy in which the mother or the baby may experience medical complications due to a newly developed or pre-existing disorder.

This includes conditions that could threaten the well-being of the mother or child, such as diabetes, high blood pressure, heart problems, a history of miscarriage, preeclampsia, symptoms of premature labor or the expectation of multiple births.

“As many as 10% of pregnancies are considered high risk, but with expert care, 95% of these special cases result in the birth of healthy babies,” says Major.

“We work with our high-risk moms to weigh the risks and benefits of the vaccines.”

What do patients want to know?

“Pregnant patients primarily want to know that the vaccine will not harm their unborn babies,” she says. “I try to reassure them that based on how the vaccines work, I don’t believe there is any biological reason for concern about its safety in pregnancy.”  

Breastfeeding women should also get the vaccine to protect themselves from getting COVID-19. The way the vaccine works, there’s no reason to suspect that it gets into breast milk and can in anyway get to the child, she adds. And women who are planning to get pregnant should go ahead and get vaccinated if given the opportunity. If they become pregnant between the first and second vaccine dose, they should complete the series.

“Overall, COVID-19 vaccination for pregnant and nursing women, especially in high-risk groups, has many potential benefits,” says Major. “We’ll know more definitively once data from the new trial is available."


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