New research provides reassuring evidence for pregnant women concerned about COVID-19 vaccination safety. A case-control study published in Obstetrics & Gynecology on May 2, 2025, found no association between COVID-19 vaccination during pregnancy and spontaneous abortion (miscarriage).
The study, conducted through the Vaccine Safety Datalink (VSD), followed nearly 900 women across eight healthcare systems, comparing 296 clinically confirmed miscarriages with 592 matched live births. After careful analysis, researchers found no evidence that vaccination increased miscarriage risk, regardless of vaccine manufacturer, number of doses, or timing of vaccination.
“We hope that data such as ours are providing increasing reassurance that the vaccine is safe, and that we will see those rates go up,” said Dr. Sangini S. Sheth, the study’s principal investigator and associate professor of obstetrics, gynecology, and reproductive sciences at Yale.
This research addresses a critical gap in vaccine safety knowledge. While COVID-19 vaccination rates have improved overall, pregnant women continue to have among the lowest vaccination rates, with less than 15% receiving the vaccine during the 2023-2024 season, according to VSD surveillance data.
Rigorous Methods Strengthen Confidence
Unlike previous studies that relied solely on diagnostic codes from electronic health records, this study took the extra step of having medical experts review and confirm each miscarriage case. This clinical verification process provided more precise dating of pregnancies and reduced the possibility of misclassification that could have skewed results.
The research team matched women who experienced miscarriages with those who had live births based on key factors including maternal age, pregnancy start date, and healthcare site. The analysis accounted for multiple potential confounding factors such as maternal age, race, ethnicity, socioeconomic status, and pre-existing health conditions.
After adjusting for these variables, researchers found no significant association between miscarriage and COVID-19 vaccination (adjusted odds ratio 0.85). Similarly, there was no association with specific vaccine manufacturers (Moderna or Pfizer-BioNTech) or with receiving the vaccine within six weeks before a miscarriage.
Addressing Persistent Vaccine Hesitancy
Despite consistent recommendations from the Advisory Committee on Immunization Practices since December 2020, COVID-19 vaccination rates among pregnant women remain suboptimal. Common concerns include worries about side effects and perceived lack of safety data.
The study’s findings are particularly important because the vaccine exposure window included the critical early phases of pregnancy when fertilization, implantation, and embryonic development occur. These results complement previous research showing no increased risk of other adverse pregnancy outcomes such as stillbirth or preterm birth after vaccination.
Dr. Sheth emphasized the practical implications: “This is a rigorously conducted study that continues to show that the COVID-19 vaccines are safe during pregnancy. For women who are early in pregnancy or those who are thinking about getting pregnant, given the risks of COVID-19 disease, they should feel encouraged to go ahead and get vaccinated if they are not already.”
COVID-19 Risks During Pregnancy
The research comes against the backdrop of well-documented risks that COVID-19 infection poses to pregnant women. Studies have shown that pregnant women with COVID-19 face increased rates of hospitalization, ICU admission, and need for ventilation compared to non-pregnant women.
Additionally, COVID-19 infection during pregnancy is associated with a higher risk of complications including preterm birth, stillbirth, and maternal death. These risks provide strong motivation for improving vaccination rates in this vulnerable population.
Study Limitations
The researchers acknowledged several limitations to their work. The study included fewer confirmed miscarriage cases than initially anticipated after medical record review, which limited statistical power to detect smaller effects. Additionally, miscarriages occurring before six weeks of gestation were not included because they often occur without clinical recognition and are difficult to date accurately.
The study population was primarily insured and may not fully represent all geographic regions of the United States. The researchers suggest that future studies should examine more diverse populations and include larger sample sizes.
Looking Forward
As COVID-19 continues to evolve and vaccination recommendations are updated, this research provides an important piece of evidence supporting the safety of vaccination during pregnancy. The findings should help healthcare providers offer more confident vaccine counseling to patients who are pregnant or planning pregnancy.
The researchers conclude that strengthening the evidence supporting COVID-19 vaccine safety can help address hesitancy and improve the effectiveness of recommendations delivered to patients. Prior research has consistently shown that a strong recommendation from a healthcare provider significantly influences vaccine acceptance.
With this additional safety data in hand, medical professionals hope to see increased vaccination rates among pregnant women, potentially preventing serious illness and complications for both mothers and babies.
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