A study of over 6,500 mothers found that COVID-19 vaccination during pregnancy significantly lowered the risk of preeclampsia, a dangerous blood-pressure disorder.
TheDigger Intelligence Unit
Pregnant women who roll up their sleeves for COVID-19 vaccines may be doing more than protecting themselves from the virus — they’re slashing their risk of preeclampsia, a dangerous complication that threatens mothers and babies. A sweeping international study shows vaccination, especially with boosters, sharply lowers the odds of this life‑threatening condition.
Studies have consistently shown thatThe new findings indicate that during the pandemic, pregnant women who contracted COVID-19 had a 45% higher risk of preeclampsia compared to those who did not contract the virus. For unvaccinated women who became infected with COVID-19, the risk increased by 78%.
Vaccination, meanwhile, lowered the risk of preeclampsia. Among people who completed an initial COVID-19 vaccine regimen and received an updated booster shot, the risk of preeclampsia decreased by 33% compared with unvaccinated individuals. Among people with preexisting medical conditions, such as diabetes, who got a booster dose, the risk decreased by 58%, also in comparison to the unvaccinated group.
If these findings are confirmed, they would be a “breakthrough” in understanding the potential links between preeclampsia and viruses, co-lead study author Dr José Villar, a professor of perinatal medicine at the University of Oxford, told Live Science.
“A protective effect”
About 3% to 8% of pregnant people develop preeclampsia, typically in the second half of pregnancy or shortly after childbirth. Preeclampsia is marked by 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 headaches, 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 to the placenta’s blood supply. It can sometimes progress to eclampsia, which involves brain swelling, seizures or coma. Both preeclampsia and eclampsia can be life-threatening for both the mother and the baby.
Scientists don’t know exactly what causes preeclampsia. There’s some research to suggest it arises from abnormal development of the placenta, but it’s not completely clear whether placental dysfunction drives preeclampsia or is a consequence of it. That said, there is emerging evidence that viral infections, such as COVID-19, may play a role in some cases by triggering changes in the immune system and causing blood-vessel dysfunction, the key process behind preeclampsia symptoms.
Villar’s team speculated that COVID-19 vaccines might help curb that risk by lowering the odds of COVID-19 infection and severe illness. They also theorised that vaccination may boost the immune system overall, thereby protecting against other infections and vascular damage.
For the study, published Feb. 18 in eClinicalMedicine, researchers analysed data from over 6,500 pregnant women in 18 countries during 2020–2022. Of these women, one-third were diagnosed with COVID-19 during pregnancy. At data collection, 58% (about 3,770 women) were unvaccinated against COVID-19. Of the vaccinated women (about 2,730), 31% (about 847) received a booster dose after completing their initial vaccine series.
Vaccination seemed to offer a “protective effect” against preeclampsia, the researchers said, and booster shots added an extra defence. Notably, women who got booster shots also had lower rates of poor pregnancy outcomes overall — measured as an index score that included events like preterm birth, admission to an intensive care unit, and more — compared with unvaccinated women.
That’s in line with research published in 2024 that found women who got at least one COVID-19 shot were less likely to have preterm births, experience stillbirth, or have a baby who was small for their gestational age than unvaccinated people were.
“Vaccinations are safe and are protective for several risks,” said Dr Elena Raffetti, an assistant professor at the Karolinska Institute in Sweden and first author of the 2024 report. “There was not at all an increased risk of preeclampsia among women who were vaccinated,” added Raffetti, who was not involved in the new study.
The authors of the latest study emphasised that their findings support current vaccine guidance. The American College of Obstetricians and Gynaecologists recommends that pregnant people get an updated COVID-19 vaccine at the earliest opportunity — either while trying to get pregnant, during any trimester of pregnancy, or while breastfeeding or in the postpartum period.
The new analysis does have some limitations. For example, while the researchers tried to control for factors that could influence the results — such as the women’s ages, smoking history or health issues linked to preeclampsia, such as previous high blood pressure and diabetes — Villar said there may be other differences between the vaccinated and unvaccinated groups that contributed to their risks.
The authors suggest that future research should examine how the immune system responds to infections and vaccines, and why infections such as COVID-19 increase the risk of preeclampsia.
Villar emphasised that understanding the causes of preeclampsia could yield crucial insights into maternal and fetal health.
