New research provides reassuring evidence for pregnant women focusing on the safety of Covid-19-19 vaccination. Case control study published in Obstetrics and Gynecology On May 2, 2025, it was found that there was no association between vaccination during pregnancy and spontaneous miscarriage (miscarriage).
The study, conducted through Vaccine Safety Data Link (VSD), tracked nearly 900 women in eight healthcare systems, comparing 296 clinically confirmed miscarriages with 592 matched live births. After careful analysis, the researchers did not find that vaccination increased the risk of miscarriage, regardless of vaccine manufacturer, dose quantity or vaccination time.
“We hope our data will make the vaccine safe and will increase the assurance of vaccines,” said Sangini S. Sheth, Ph.D., the principal investigator of the study and associate professor of obstetrics, gynecology and reproductive sciences at Yale University.
This study addresses a key gap in vaccine safety knowledge. According to VSD surveillance data, although the vaccination rate for COVID-19-19 has increased overall, pregnant women are still in the lowest vaccination rate, with vaccination rate less than 15% in the 2023-2024 season.
Strict approach enhances confidence
Unlike previous studies that rely solely on diagnostic codes for electronic health records, this study took additional steps to allow medical experts to review and confirm each case of miscarriage. This clinical validation process provides more precise expectations of pregnancy and reduces the possibility of misclassification of outcomes that may bias results.
The research team matched those women based on key factors including maternal age, pregnancy start date and health care site with those women who had live streaming. This analysis explains a number of potential confounding factors such as maternal age, race, race, socioeconomic status, and pre-existing health conditions.
After adjusting for these variables, the researchers found no significant association between miscarriage and COVID-19 vaccination (adjusted odds ratio 0.85). Likewise, there is no association with a specific vaccine manufacturer (ModernA or Pfizer-biontech) and has not received the vaccine within the six weeks before the miscarriage.
Solve ongoing vaccine hesitation
Despite unanimous recommendations from the Advisory Committee since December 2020, vaccination rates for pregnant women remain the best. Common concerns include concerns about side effects and the perception that there is a lack of security data.
The findings of this study are particularly important because the vaccine exposure window includes the critical early stages of pregnancy when fertilization, implantation and embryonic development occur. These results complement previous studies showing that there is no increased risk of other adverse pregnancy outcomes after vaccination, such as stillbirth or premature birth.
Dr. Sheth highlighted the actual implications: “This is a rigorous study that continues to show that the Covid-19 vaccine is safe during pregnancy. For women who are early in pregnancy or who are considering pregnancy, given the risk of Covid-19 disease, vaccines should be encouraged and received if they have not already.”
Risks during COVID-19 pregnancy
This study is based on a well-documented risk, which constitutes a co-infection in pregnant women. Research shows that pregnant women with COVID-19 face increased hospitalization rates, ICU admission and ventilation needs compared to non-pregnant women.
In addition, Covid-19 infection during pregnancy is associated with a higher risk of complications, including premature birth, stillbirth and maternal death. These risks provide a strong impetus for increasing vaccination rates in vulnerable populations.
Research limitations
The researchers acknowledge that their work has some limitations. The study confirmed fewer cases of miscarriage than initially expected after medical record review, which limited the impact of statistical power detection. In addition, miscarriages that occur before six weeks of gestation are not included, as they often occur without clinical identification and are difficult to date accurately.
The study population is primarily insured and may not fully represent all geographical areas of the United States. The researchers believe that future studies should examine more populations and include larger sample sizes.
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With COVID-19 evolving and vaccination recommendations updated, this study provides important evidence to support the safety of vaccination during pregnancy. These findings should help healthcare providers provide more confident vaccine counseling for patients who are pregnant or planning to get pregnant.
The researchers concluded that strengthening evidence supporting the safety of Covid-19 vaccines could help address hesitation and improve the effectiveness of advice provided to patients. Previous studies have shown that strong advice from healthcare providers can significantly affect vaccine acceptance.
With the safety data at hand, medical professionals want to see an increase in vaccination rates in pregnant women, which may prevent serious illness and complications in mothers and babies.
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