The CDC encouraged pregnant and breastfeeding women to get vaccinated against COVID-19 as researchers from the agency reported what they called “reassuring” data Wednesday on the safety of the vaccines.
An analysis of nearly 2,500 pregnant people who received a COVID-19 messenger RNA vaccine before 20 weeks of pregnancy found no increased risk for miscarriage, the CDC researchers reported in a preprint study.
The researchers noted that, because pregnant women were not included in trials of COVID-19 vaccines, data on their safety in this population have been limited, although “there is no compelling biological reason to expect that mRNA COVID-19 vaccination (either preconception or during pregnancy) presents a risk to pregnancy,” they wrote.
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Still, vaccine uptake has been slow among pregnant women in the United States, especially among Hispanic and non-Hispanic Black women.
“CDC encourages all pregnant people or people who are thinking about becoming pregnant and those breastfeeding to get vaccinated to protect themselves from COVID-19,” CDC Director Rochelle P. Walensky, MD, MPH, said in a statement.
“The vaccines are safe and effective, and it has never been more urgent to increase vaccinations as we face the highly transmissible Delta variant and see severe outcomes from COVID-19 among unvaccinated pregnant people.”
For the study, CDC research fellow Lauren Head Zauche, PhD, RN, CPNP-PC, and colleagues assessed data from a smartphone-based surveillance system on 2,456 pregnant women who received at least one dose of an mRNA COVID-19 vaccine prior to 20 weeks’ gestation and who did not report a loss of pregnancy before 6 weeks gestation.
According to the researchers, among all pregnancies in high-income countries, about 11% to 16% end in spontaneous abortion (SAB).
The new study assessed participants from 6 to 19 weeks’ gestation. Among the 2,456 participants, 2,020 were known to be pregnant at 20 weeks’ gestation, and 165 reported pregnancy loss, with 154 occurring prior to 14 weeks’ gestation.
Overall, the risk for SAB from 6 to 19 weeks’ gestation among women who received one of the vaccines was 14.1% (95% CI, 12.1-16.1%). \
When stratified for age, the risk was 9.8% among those aged 20 to 29 years (95% CI, 5.9-12.4%); 13% among those aged 30 to 34 years (95% CI, 10.1-15.8%); 16.7% among those aged 35 to 39 years (95% CI, 12.5-20.6%); and 28.8% among those aged older than 40 years (95% CI, 16.8-39.1%).
“These data suggest that the cumulative risk of an SAB from 6 to 19 weeks’ gestation after receipt of an mRNA COVID-19 vaccine is within the expected range based on previous SAB studies,” the authors wrote.
“Confirmation of these results is needed from observational studies that include unvaccinated pregnant people.”