Among pregnant women who received COVID-19 vaccines manufactured by Pfizer Inc and BioNTech SE or Moderna Inc and who signed up for an online survey, side effects were no different than what has been seen in the general population, researchers reported in The New England Journal of Medicine.
But they noted that data of this nature is still sparse.
They looked at responses from smartphone users who participated in the U.S. Centers for Disease Control and Prevention (CDC) "v-safe" program, which collects information on COVID-19 vaccination experiences.
Compared to non-pregnant women, the 35,691 pregnant responders reported more injection site pain but fewer headaches, muscle aches, chills, and fevers.
Among 3,958 women who signed up for a CDC pregnancy registry, no one vaccinated in the first trimester has given birth yet.
The Vaccine Adverse Event Reporting System (VAERS), run jointly by the CDC and the U.S. Food and Drug Administration, has recorded 46 miscarriages potentially related to COVID-19 vaccination, including 37 in the first trimester, the researchers said.
"Early data from the v-safe surveillance system, the v-safe pregnancy registry, and the VAERS do not indicate any obvious safety signals with respect to pregnancy or neonatal outcomes associated with Covid-19 vaccination in the third trimester of pregnancy," researchers concluded.