COVID-19 Vaccines Not Linked to Miscarriage in Surveillance Study

Pregnant patient receives COVID-19 vaccine
Experts discuss emerging safety data on administration of COVID-19 mRNA vaccines during pregnancy.

Administration of the Pfizer-BioNTech and Moderna mRNA COVID-19 vaccines during pregnancy was not associated with an increased risk of miscarriage based on new surveillance data published in a research letter in JAMA.1 The findings support vaccine recommendations for pregnant patients from the American College of Obstetricians and Gynecologists (ACOG) and Centers for Disease Control and Prevention (CDC).2,3

“This report provides additional reassuring news about the safety of COVID vaccines, particularly mRNA vaccine during pregnancy,” commented Denise J. Jamieson, MD, MPH, who is not affiliated with this study. “This report found no increased risk of spontaneous abortion among those who were vaccinated.” Dr Jamieson is coauthor of the ACOG practice guidance on COVID-19 vaccination in pregnancy and a member of the ACOG Immunization, Infectious Disease, and Public Health Preparedness Expert Work Group.

Study Design

Elyse Kharbanda, MD, and colleagues analyzed data from 105,446 patients with pregnancies of 6 to 19 weeks’ gestation between December 15, 2020, and June 28, 2021. The patients were seen at 1 of 8 health systems (Kaiser Permanente: Washington, Northwest, Northern California, Southern California, and Colorado; DenverHealth; HealthPartners; and Marshfield Clinic, Wisconsin) that participate in the CDC-funded Vaccine Safety Datalink.

Vaccination rates were as follows: 7.8% received 1 or more Pfizer-BioNTech vaccines, 6.0% received 1 or more Moderna vaccines, and 0.5% received the Janssen COVID-19 vaccine. Vaccination data were derived from electronic health records, medical and pharmacy claims, and regional or state immunization information systems.

Key Findings

Patients with spontaneous abortions (n=13,160) did not have an increased odds of exposure to a COVID-19 mRNA vaccine exposure in the prior 28 days compared with women with ongoing pregnancies (n=92,286) after adjusting for maternal age and other risk factors for miscarriage (odds ratio, 1.02; Table). The results were consistent when the data was analyzed by vaccine type (ie, Pfizer-BioNTech and Moderna COVID-19 vaccines). The researchers were not able to assess the risks of the Janssen COVID-19 vaccine given the small number of patients who received this vaccine in the study database, the researchers noted. 

Elyse Kharbanda, MD

“This study adds to the growing body of literature on the safety of COVID-19 vaccination when administered early in pregnancy,” said Dr Kharbanda, who is a senior investigator at HealthPartners Institute. “It is important to continue to discuss risks and benefits of vaccination with your patients, and to address misconceptions or myths when they are raised. This study should help address concerns among pregnant patients regarding specific risks of pregnancy loss or miscarriage following [mNRA] COVID-19 vaccination.”

Strengths of the study include the large number of pregnant patients studied and the use of analytic approaches to adjust for other spontaneous abortion risk factors, Dr Kharbanda said. Study limitations include lack of chart confirmation of gestational age of spontaneous abortions and ongoing pregnancies, the possibility that vaccinations may have been missed, and lack of data on potential confounding factors such as prior pregnancy history.

ACOG Expert Discusses Patient Education Strategies

When speaking with patients about the COVID-19 vaccines, Dr Jamieson discusses the potential efficacy of the vaccine; the potential risk and severity of maternal COVID-19 disease, including the effects of disease on the fetus and newborn; and the safety of the vaccine for the pregnant patient and the fetus.

“I explain that there is no evidence of adverse maternal or fetal effects from vaccinating pregnant individuals with COVID-19 vaccine and there is excellent evidence that these vaccines work to protect pregnant persons from severe disease from COVID.  There is also a growing body of data that demonstrate the safety of these vaccines in pregnancy,” said Dr Jamieson, who is James Robert McCord Professor and chair of the Department of Gynecology & Obstetrics at Emory University School of Medicine in Atlanta, Georgia.

Both ACOG and the Society for Maternal-Fetal Medicine (SMFM) recommend that all pregnant individuals be vaccinated against COVID-19.2 “The organizations’ recommendations in support of vaccination during pregnancy reflect evidence demonstrating the safe use of the COVID-19 vaccines during pregnancy from tens of thousands of reporting individuals over the last several months,” Dr Jamieson said. “These latest findings support that recommendation.”

CDC Pregnancy Recommendations

The CDC recommends COVID-19 vaccination for all people 12 years and older, including people who are pregnant, breastfeeding, trying to conceive, or planning to become pregnant in the future.3 Current data suggest that the benefits of receiving a COVID-19 vaccine outweigh any known or potential risks of vaccination during pregnancy, according to the CDC.

Patients who are pregnant or were recently pregnant (for at least 42 days following the end of pregnancy) are at increased risk for severe illness from COVID-19 compared with people who are not pregnant, according to the CDC.3 Pregnant people with COVID-19 are also at increased risk for preterm birth (delivering the baby earlier than 37 weeks) and might be at increased risk for other poor pregnancy outcomes.

Dr Lipkind reported serving on the Pfizer independent external data monitoring committee for the COVID-19 vaccine. Dr Naleway and Dr Vesco reported receiving research funding from Pfizer for an unrelated study.


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

2. The American College of Obstetricians and Gynecologists. Practice Advisory: COVID-19 Vaccination Considerations for Obstetric–Gynecologic Care. December 2020.

3. Centers for Disease Control and Prevention. Pregnant and recently pregnant people. Updated August 16, 2021. Accessed September 9, 2021.

This article originally appeared on Clinical Advisor