COVID-19 vaccination during pregnancy may cut risk of preeclampsia
Catching COVID-19 during pregnancy significantly increases the risk of preeclampsia linked to a blood pressure disorder – but getting vaccinated protects against this serious pregnancy complication, new research suggests.
Studies have consistently shown that COVID-19 may worsen pregnancy outcomes. The new findings suggest that, during the pandemic, coronavirus infection increased the risk of preeclampsia by 45% in pregnant women who contracted it, compared to those who did not contract it. Unvaccinated women who caught COVID-19 saw their risk increase by 78%.
If these results are confirmed, they would constitute a “breakthrough” in understanding the potential links between preeclampsia and viruses, co-senior author of the study Dr José Villarprofessor of perinatal medicine at the University of Oxford, told Live Science.
“A protective effect”
About 3% to 8% of pregnant people develop preeclampsia, usually in the second half of pregnancy or shortly after delivery. Preeclampsia is marked by persistent high blood pressure and, often, by the presence of proteins in the urine, a sign of kidney damage. It may also cause vision problems, vomiting, severe headache, or sudden swelling of the face, hands, or feet.
Preeclampsia can cause serious complications, including liver and kidney damage, pressure on the heart, and disruption of blood supply to the placenta. This can sometimes progression to eclampsiawhich involves brain swelling, seizures or coma. Preeclampsia and eclampsia can be life-threatening for both mother and baby.
Scientists don’t know exactly what causes preeclampsia. Some research suggests that this results from abnormal development of the placenta, but it is not entirely clear whether placental dysfunction causes preeclampsia or is a consequence of it. That said, it is taking shape evidence that viral infectionslike COVID-19, can play a role in some cases by triggering changes in the immune system and causing blood vessel dysfunction, the key process causing the symptoms of preeclampsia.
Villar’s team hypothesized that COVID-19 vaccines could help reduce this risk by reducing the chances of infection and severe illness from COVID-19. They also hypothesized that vaccination could strengthen the immune system as a whole, protecting against further infections and damage to blood vessels.
For the study, published February 18 in the journal eMedicineClinicalResearchers analyzed data from more than 6,500 women in 18 countries who were pregnant between 2020 and 2022. A third of participants were diagnosed with COVID-19 during pregnancy. About 58% were not vaccinated against COVID-19 at the time their data was collected. Of the remaining women, approximately 31% received a booster dose in addition to completing their initial vaccination series.
Vaccination appears to offer a “protective effect” against preeclampsia, researchers say, and booster shots add additional defense. Notably, women who received booster shots also had lower rates of poor pregnancy outcomes overall – measured by an index including events such as premature birth, admission to an intensive care unit, etc. – compared to unvaccinated women.
This is consistent with research published in 2024 which found that women who received at least one COVID-19 shot were less likely to give birth prematurely, have a stillbirth, or have a baby small for their gestational age than unvaccinated people.
“Vaccines are safe and protect against several risks,” said Dr Elena Raffettiassistant professor at the Karolinska Institutet in Sweden and first author of the 2024 report. “There was no increased risk of preeclampsia in vaccinated women at all,” added Raffetti, who was not involved in the new study.
The authors of the latest study emphasized that their results support current vaccine guidelines. THE The American College of Obstetricians and Gynecologists recommends that pregnant people receive an updated COVID-19 vaccine as soon as possible – either when trying to get pregnant, during any trimester of pregnancy, or while breastfeeding or in the postpartum period.
The new analysis has some limitations. For example, while researchers tried to control for factors that might influence the results — such as women’s age, smoking history, or preeclampsia-related health problems, such as high blood pressure and diabetes — Villar said there could be other differences between the vaccinated and unvaccinated groups that contributed to their risks.
The study authors said future research into the causes of preeclampsia should focus on how the immune system responds to both infections and vaccines, and why infections like COVID-19 appear to increase the risk of this disease.
Villar noted that much is still unknown about the causes of preeclampsia, meaning any new analysis can help researchers understand this “major disease affecting the mother and fetus.”
This article is for informational purposes only and is not intended to offer medical advice.
Cavoretto, PI et al. (2026). Covid-19 vaccination status during pregnancy and risk of preeclampsia: the pandemic era cohort of the INTERCOVID consortium. eMedicineClinical103785. https://doi.org/10.1016/j.eclinm.2026.103785
