The COVID-19 vaccine shows no link to pre-term births, a new CDC study concludes

By Tien Le

Published January 5, 2022 at 3:39 PM CST

A health worker administers a dose of a Moderna COVID-19 vaccine during a vaccination clinic at the Norristown Public Health Center in Norristown, Pa., Tuesday, Dec. 7, 2021.

As many as two-thirds of pregnant women remain unvaccinated — many out of concern that the vaccine is not safe.

In September, the Centers for Disease Control and Prevention urged those expecting a child to get a vaccine because COVID-19 can cause health complications for both the mother and baby.

Now, a new CDC study released on Tuesday of more than 40,000 women has found that the COVID-19 vaccine does not add to the risk of delivering a baby prematurely or delivering a child who is born smaller or less developed than expected, also known as small-for-gestational-age.

The study examined the pregnancies of just over 46,000 women, about 10,000 of whom received at least one dose of a COVID-19 vaccine during their pregnancy between December 2020 and July 2021. Nearly every woman in the study received an mRNA vaccine from either Moderna or Pfizer-BioNTech, while about 4% received a dose from Johnson & Johnson.

The researchers found that among all the pregnancies, 6.6% percent of newborn babies in the study were born prematurely. Among unvaccinated women, the rate was 7%. For those who received at least one vaccine dose during the course of their pregnancy, it was 4.9%.

When it came to babies who were born small for their gestational age, the researchers found no difference between the vaccinated and the unvaccinated. The rate for both groups was 8.2%.

Nearly every woman in the study was vaccinated in either the second or third trimester; only about 1% received a vaccine in the first trimester.

The authors of the study write that their findings "reinforce the importance of communicating the risks for COVID-19 during pregnancy, the benefits of vaccination, and information on the safety and effectiveness of COVID-19 vaccination during pregnancy."

They point out, for example, that the absolute risk for severe morbidity related to COVID-19 is low for pregnant people. But they also note that pregnant women with symptomatic COVID-19 have a 70% increased risk of death compared to women who are not pregnant.

Compared with women who are not pregnant, pregnant women with a symptomatic case of COVID-19 also have more than twice the risk for being admitted into an intensive care unit.

The authors say their findings "add to the evidence supporting the safety of COVID-19 vaccination during pregnancy."

Tien Le is an intern on NPR's News Desk.