COVID vaccination in pregnancy appears to lower preeclampsia risk and not increase miscarriage risk

Two recent studies report that COVID-19 vaccination in pregnancy was associated with lower odds of preeclampsia—especially with a booster—and found no increased risk of miscarriage before 20 weeks among recipients of Pfizer or Moderna vaccines.

Two new studies examined pregnancy outcomes after COVID-19 vaccination and report results relevant to preeclampsia and early pregnancy loss. One was an international analysis from the INTERCOVID consortium published in eClinicalMedicine that compared outcomes in two cohorts from 2020 and 2022. The other was an update from the US Centers for Disease Control and Prevention published in Vaccine, using the COVID-19 Vaccine Pregnancy Registry from December 2020 to June 2021. Both studies focused on mRNA vaccines and reported findings that bear on safety and related pregnancy risks. Key findings: - INTERCOVID study: researchers analyzed 6,527 pregnant women from 18 countries across two cohorts and reported that full vaccination was associated with a 15% reduction in odds of preeclampsia (adjusted odds ratio 0.85) and a booster dose with a 33% reduction (aOR 0.67). - In the INTERCOVID cohort, 33.2% tested positive for COVID-19 and 57.5% were unvaccinated; among the 2,774 vaccinated women, 64.7% received an mRNA vaccine and 30.6% had a booster (about two-thirds of boosters were mRNA). - INTERCOVID additional results: COVID-19 infection was associated with higher odds of preeclampsia (aOR 1.45), with a larger effect in unvaccinated women (aOR 1.78); vaccination with a booster was linked to lower odds of maternal and perinatal disease, death, and preterm birth (reported aORs 0.68, 0.71, and 0.67 respectively). - CDC Vaccine study: investigators reviewed 12,907 pregnancies and found a cumulative miscarriage risk of 10.8% between 6 and 20 weeks after at least one dose of a monovalent mRNA vaccine, with similar risk between Moderna and Pfizer recipients (adjusted hazard ratio 0.92). - CDC study notes and sensitivity analyses: including miscarriages before 6 weeks raised the cumulative estimate to 13.5%, and excluding those fully vaccinated before the last menstrual period yielded 9.7%; the cohort was fairly homogenous (about 79% White and 77% in their 30s). Summary: The INTERCOVID analysis associates COVID-19 vaccination in pregnancy with lower odds of preeclampsia, with stronger associations reported for booster doses and among some subgroups, and the CDC registry update found no increased risk of miscarriage before 20 weeks after mRNA vaccination. Study authors called for further research into preeclampsia mechanisms and noted limits on generalizability for the registry data. Undetermined at this time is how these findings will influence specific public health policies or clinical recommendations.