COVID-19 vaccination during pregnancy: No link to spontaneous abortion

Researchers conducting a case-control surveillance of COVID-19 vaccination during pregnancy found that spontaneous abortions did not increase as a result of vaccinations.

The results of a case-control surveillance of COVID-19 vaccination during pregnancy and spontaneous abortion found that spontaneous abortions did not increase as a result of COVID-19 vaccinations, according to Elyse O. Kharbanda, MD, MPH, HealthPartners Institute, Minneapolis, Minnesota, first author of the study.1 

According to investigators, this is good news considering the severe maternal morbidity associated with the COVID-19 infection during pregnancy.2

The investigators included data from 8 health systems over 7 4-week surveillance periods from December 15, 2020, through June 28, 2021.

A validated pregnancy algorithm was used that included diagnostic and procedural codes and electronic health record data to identify and assign gestational ages for spontaneous abortions and ongoing pregnancies; the data on vaccinations were from electronic health records, medical and pharmacy claims, and regional/state immunization systems.

Ongoing pregnancies between 6 and 19 weeks’ gestation were identified on the last day of each 4-week surveillance period (index date). Spontaneous abortions were assigned to a 4-week surveillance period based on their outcome date.

The authors analyzed the odds of receiving a COVID-19 vaccine in the 28 days before a spontaneous abortion compared with the odds of receiving a COVID-19 vaccine in the 28 days before the index dates for ongoing pregnancies.

The spontaneous abortions and ongoing pregnancies were assigned to gestational age groups of 6-8, 9-13, and 14-19 weeks), surveillance periods, site, maternal age groups (16-24, 25-34, and 35-49 years), number of antenatal visits (≤1 or ≥2), and race and ethnicity.

A total of 105,446 pregnancies were identified; of those, 13,160 spontaneous abortions occurred and 92,286 pregnancies continued.

Almost 7.8% of women received 1 or more BNT162b2 (Pfizer-BioNTech) vaccines; 6.0% 1 or more mRNA-1273 (Moderna) vaccines; and 0.5% the Ad26.COV.2.S (Janssen) vaccine during pregnancy and before 20 weeks’ gestation. More women aged 35 through 49 years had a spontaneous abortion (38.7%) compared with those with ongoing pregnancies (22.3%).

“A COVID-19 vaccine was received within 28 days prior to an index date among 8.0% of ongoing pregnancy periods vs 8.6% of spontaneous abortions.

Spontaneous abortions did not have an increased odds of exposure to a COVID-19 vaccination in the prior 28 days compared with ongoing pregnancies (adjusted odds ratio, 1.02; 95% [confidence interval, 0.96-1.08).

Results were consistent for mRNA-1273 and BNT162b2 and by gestational age group,” the authors reported.

Too few women received the Ad26.COV.2.S vaccine to analyze the risks of an association with spontaneous abortions.

The authors concluded that despite some study limitations, they believe the data can be used to advise patients about receiving vaccinations for COVID-19.



1. Kharbanda EO, Haapala J, DeSilva et al. Spontaneous abortion following COVID-19 Vaccination during Pregnancy. JAMA Published online September 8, 2021. doi:10.1001/jama.2021.15494

2. Ko JY, DeSisto CL, Simeone RM, et al. Adverse pregnancy outcomes, maternal complications, and severe illness among US delivery hospitalizations with and without a coronavirus disease 2019 (COVID-19) diagnosis. Clin Infect Dis 2021;73(suppl 1):S24-S31. doi:10.1093/cid/ciab344