Catching COVID-19 during pregnancy significantly increases the risk of the blood pressure disorder preeclampsia — but getting vaccinated protects against this serious pregnancy complication, new research finds.
Studies have consistently shown that COVID-19 can worsen pregnancy outcomes. The new findings suggest that the coronavirus infection during the pandemic increased the risk of preeclampsia by 45% among pregnant women who received it, compared to those who did not. Unvaccinated women who contracted covid-19 saw their risk increase by 78%.
If confirmed, these findings would be a “breakthrough” in understanding the potential links between preeclampsia and the virus, co-lead study author Dr. José Villara professor of perinatal medicine at the University of Oxford, told LiveScience.
“A protective effect”
About 3% to 8% of pregnant women develop preeclampsia, usually in the second half of pregnancy or shortly after birth. Preeclampsia is marked with persistent high blood pressure and often protein in the urine, which is a sign of kidney damage. It can also cause vision problems, vomiting, severe headache or sudden swelling of the face, hands or feet.
Preeclampsia can cause serious complications, including damage to the liver and kidneys, strain on the heart and disruption of the placenta’s blood supply. It can sometimes progress to eclampsiainvolving swelling of the brain, seizures or coma. Both preeclampsia and eclampsia can be life-threatening for both mother and baby.
Scientists don’t know exactly what causes preeclampsia. There is some research that suggests it arises from abnormal development of the placenta, but it is not entirely clear about placental dysfunction drives preeclampsia or is a consequence of it. That being said, it shows up evidence of viral infectionsfor example, COVID-19, can play a role in some cases by triggering changes in the immune system and causing cardiovascular dysfunction, the key process behind preeclampsia symptoms.
Villar’s team speculated that COVID-19 vaccines could help mitigate this risk by reducing the chances of COVID-19 infection and serious illness. They have also theorized that vaccination can boost the immune system overall, thereby protecting against other infections and damage to the blood vessels.
For the study, which was published on February 18 in the journal eClinicalMedicinethe researchers analyzed data from more than 6,500 women in 18 countries who were pregnant between 2020 and 2022. A third of the participants were diagnosed with COVID-19 during pregnancy. About 58% were unvaccinated for COVID-19 when their data was collected. Among the remaining women, approx. 31% a booster dose in addition to completing their original vaccination series.
Vaccination appeared to offer a “protective effect” against preeclampsia, the researchers said, and booster shots provided an additional defense. Notably, women who received booster shots also had lower rates of poor pregnancy outcomes overall — measured as an index score that included events such as premature birth, intensive care unit admission and more — compared to unvaccinated women.
It is in line with research published in 2024 who found that women who received at least one COVID-19 shot were less likely to have premature births, experience a stillbirth, or have a small-for-gestational-age baby than unvaccinated people.
“Vaccinations are safe and protect against multiple risks,” said Dr. Elena Raffettiassistant professor at Karolinska Institutet in Sweden and first author of the 2024 report. “There was no increased risk of preeclampsia at all among women who were vaccinated,” added Raffetti, who was not involved in the new study.
The authors of the latest study emphasized that their findings support current vaccine guidance. The The American College of Obstetricians and Gynecologists recommends that pregnant women receive an updated COVID-19 vaccine as early as possible – either while trying to conceive, in any trimester of pregnancy, or while breastfeeding or in the postpartum period.
The new analysis has some limitations. For example, while the researchers tried to control for factors that could affect the results — such as the women’s age, smoking history or health problems related to preeclampsia, such as pre-existing high blood pressure and diabetes — Villar said there may be other differences between the vaccinated and unvaccinated groups that contributed to their risk.
The study authors said future research into preeclampsia’s causes should focus on how the immune system responds to both infections and vaccines, and why infections such as COVID-19 appear to increase the risk of the condition.
Villar noted that much remains unknown about what causes preeclampsia, meaning any new insight could help researchers understand this “major disease that affects the mother and the fetus.”
This article is for informational purposes only and is not intended to provide medical advice.
Cavoretto, PI, et al. (2026). Covid-19 vaccination status during pregnancy and preeclampsia risk: the pandemic-era cohort of the INTERCOVID consortium. eClinicalMedicine103785. https://doi.org/10.1016/j.eclinm.2026.103785
