A new study found no link between COVID-19 vaccination and the risk of miscarriage in early pregnancy.
In the case-control study, conducted across eight U.S. health care systems, investigators analyzed medical records from 888 pregnant patients—including 296 women who experienced spontaneous abortion between 6 and less than 20 weeks of gestation and 592 matched controls with live births. The match was based on maternal age, location, and pregnancy date.
The investigators evaluated whether receiving a COVID-19 vaccine during early pregnancy was associated with an increased risk of spontaneous abortion. Vaccine exposure was tracked from the start of pregnancy to the date of miscarriage or the corresponding gestational age in matched controls. Vaccination data were obtained from electronic health records, insurance claims, and immunization registries.
Among the participants, 17.1% received at least one COVID-19 vaccine dose during pregnancy. Exposure rates were similar between the spontaneous abortion group (15.9%) and the live birth group (17.7%). The adjusted odds ratio (OR) for any vaccine exposure was 0.85 (95% confidence interval = 0.56–1.30), showing no statistically significant association.
Analyses by dose number also showed no increased risk. The adjusted OR was 0.81 for one dose and 0.84 for two doses. When evaluating vaccine type, the adjusted OR was 0.59 for Moderna and 0.97 for Pfizer-BioNTech. No increased risk was observed for vaccination within 6 weeks prior to the miscarriage or index date (adjusted OR = 0.87).
To improve data accuracy, the investigators manually reviewed medical records to confirm pregnancy outcomes and gestational age. This clinical adjudication minimized the risk of outcome misclassification. Live births were also confirmed using standardized birth data and gestational dating protocols.
Vaccinated individuals were generally older and more likely to live in areas with lower poverty. These variables were controlled by statistical models.
Although the number of confirmed spontaneous abortion cases was lower than anticipated, the investigators retained sufficient power to detect moderate risk differences. The investigators concluded that COVID-19 vaccination during early pregnancy wasn't associated with an increased risk of miscarriage.
The findings contributed to the growing body of research supporting the safety of COVID-19 vaccines in pregnancy.
The authors reported no conflicts of interest.
Source: Obstetrics & Gynecology