More evidence reinforces COVID-19 vaccination safety for expectant mothers

COVID-19 vaccination during pregnancy poses no increased risk of miscarriage, as shown in a case–control study.

Looking at 296 participants who had foetal loss between 6 and less than 20 weeks of gestation and 592 matched participants whose pregnancies resulted in live birth, COVID-19 vaccination had no significant association with spontaneous abortion compared with no vaccination (adjusted odds ratio [aOR], 0.85, 95 percent confidence interval [CI], 0.56–1.30). [Obstet Gynecol 2025;doi:10.1097/AOG.0000000000005904]

The lack of association persisted regardless of the number of vaccine doses (one dose: aOR, 0.81, 95 percent CI, 0.39–1.70; two doses: aOR, 0.84, 95 percent CI, 0.51–1.38) and the type of vaccine (mRNA-1273: aOR, 0.59, 95 percent CI, 0.29–1.19; BNT162b2: aOR 0.97, 95 percent CI, 0.57–1.66) received during pregnancy.

Similarly, receipt of COVID-19 vaccine within 6 weeks of outcome or index date did not alter the risk of spontaneous abortion relative to no vaccination (aOR, 0.87, 95 percent CI, 0.53–1.44).

“This study reinforces findings from prior studies demonstrating that COVID-19 vaccines have a high degree of safety during pregnancy, including during early pregnancy,” according to the study authors. [JAMA 2022;327:1469-1477; N Engl J Med 2021;385:2008-2010; JAMA Netw Open 2023;6:e2314350; Nat Commun 2022;13:6124; Pharmacoepidemiol Drug Saf 2023;32:685-693]

“Many previous studies have focused on later-pregnancy outcomes such as stillbirth or preterm birth. [Our] study focuses on early-pregnancy vaccine exposure and a single early-pregnancy outcome, with spontaneous abortion cases clinically adjudicated,” they added.

The authors emphasized that the study findings hold particular significance for pregnant women, individuals trying to become pregnant, and their clinicians, given that the COVID-19 vaccine exposure period evaluated included the critical window of fertilization, implantation, and early embryonic cell division.

“Strengthening the evidence to support safety of COVID-19 vaccination can help address vaccine hesitancy and improve the effectiveness of vaccine recommendations delivered to patients,” they said, highlighting that a clinician’s recommendation can positively influence a patient’s decision to get vaccinated.

For the case–control study, researchers used data from eight Vaccine Safety Datalink sites. Participants in the spontaneous abortion case group were matched to those in the live birth control group based on maternal age (±3 years) and pregnancy start date (±14 days). Live births were censored at the gestational age of the matched spontaneous abortion case, and that date was assigned as the index date.

Of the participants, 47 of 296 (15.9 percent) in the case group and 105 of 592 (17.7 percent) in the control group received any COVID-19 vaccine during pregnancy. The mean gestational age at spontaneous abortion was 68 days. Baseline characteristics were similar between the case and control groups. Meanwhile, compared with unvaccinated participants, those who were vaccinated were older (34.6 vs 33.5 years), less likely to identify as Hispanic (20.4 percent vs 31.0 percent), and resided in areas with lower levels of neighbourhood poverty (6.2 percent vs 7.9 percent).