Study finds COVID vaccination in female or male partners does not increase risk of miscarriage

Multiple studies have shown that the COVID-19 vaccines do not lead to infertility or pregnancy complications such as miscarriage, but many people are still wary of adverse effects from the vaccine on pregnancy.

A new study led by Boston University School of Public Health (BUSPH) researchers now provides deeper insight into the safety of COVID-19 vaccines for people planning to become pregnant.

Published in the journal Human Reproduction, the study found no increased risk of early or late miscarriage as a result of male or female partners getting a COVID-19 vaccine prior to conceiving.

The study is the first to evaluate the risk of early miscarriage (less than eight weeks' gestation) following preconception COVID-19 vaccination, as well as the first to evaluate male vaccination and miscarriage.

The researchers hope these results provide useful information for individuals planning to become pregnant, as well as their health care providers.

"These findings should be replicated in other populations, but are reassuring for couples who are planning pregnancy," says lead author Jennifer Yland, an epidemiology Ph.D. student at BUSPH at the time of the study.

For the study, Yland and colleagues analyzed survey data on COVID-19 vaccination and miscarriage among female and male participants in the BUSPH-based Pregnancy Study Online (PRESTO), an ongoing study that enrolls women trying to conceive, and follows them from preconception through six months after delivery.

Participants in this new analysis included 1,815 female individuals in the US and Canada who were followed in the study from December 2020 through November 2022. They were observed from their first positive pregnancy test until a miscarriage or other event (such as induced abortion, ectopic pregnancy, or 20 weeks' gestation)—whichever occurred first.

Among the female participants, 75% had received at least one dose of a COVID-19 vaccine by the time they became pregnant. Almost a quarter of the pregnancies resulted in miscarriage, and 75% of these miscarriages occurred prior to eight weeks' gestation, but there was no increased risk.

Risk of miscarriage was 26.6% among unvaccinated female participants, 23.9% among female participants who had received one dose of the vaccine before conception, 24.5% among those who completed a full primary series before conception, 22.1% among those who completed the vaccine series three months before conception, and 20.1% among those who received only one dose of a two-dose vaccine before conception.

"The rate of miscarriage among vaccinated individuals was not only comparable with that of PRESTO participants who conceived before the pandemic, but our data indicated a slightly lower risk of miscarriage among vaccinated individuals compared to unvaccinated individuals," Yland says.

Federal health officials continue to recommend COVID-19 vaccination to individuals planning to conceive, and stress that the benefits of receiving a COVID-19 vaccine outweigh potential risks of vaccination during preconception or pregnancy.