Severe COVID-19 carries fourfold higher risk of preterm birth and high blood pressure
A large Canadian meta-analysis has placed a sobering finding before the medical community: pregnancy and COVID-19 are not a neutral combination. Researchers at the University of Montreal, drawing on data from nearly half a million pregnant people across 42 international studies, have found that the severity of infection corresponds directly to the severity of risk — from preterm birth to dangerous elevations in blood pressure. The study arrives as a reminder that in medicine, as in life, vulnerability compounds vulnerability, and that protecting the most fragile lives sometimes means confronting uncomfortable truths about the ones carrying them.
- A fourfold increase in preterm birth and preeclampsia among severely ill pregnant patients signals that COVID-19 is not a passive presence during pregnancy — it actively disrupts the biological systems sustaining new life.
- Even symptomatic but non-severe cases double the risk of early delivery and raise the likelihood of caesarean birth by half, meaning the threat is not confined to the most critical patients.
- A leading Canadian obstetrician has raised methodological concerns, noting that the study blends confirmed and suspected cases from countries with vastly unequal healthcare access, complicating how far its conclusions can travel.
- Canadian domestic surveillance, tracking 1,800 cases nationally, has confirmed elevated hospitalization and preterm birth rates but has not yet produced a statistically significant rise in stillbirths — leaving a critical question unresolved.
- Public health guidance has nonetheless shifted: pregnant women are being urged to get vaccinated, maintain precautions, and — crucially — not allow pandemic fear to pull them away from the prenatal monitoring that catches conditions like preeclampsia before they become fatal.
Researchers at the University of Montreal have published a large-scale analysis of pregnancy outcomes during the pandemic, synthesizing data from 42 studies and nearly 440,000 pregnant people worldwide. The findings, released in the Canadian Medical Association Journal, are clear in their direction: COVID-19 infection during pregnancy raises the risks of stillbirth, preterm delivery, and preeclampsia — and the more severe the infection, the steeper those risks become.
Led by Dr. Nathalie Auger, the study found that symptomatic patients faced double the preterm birth risk of asymptomatic carriers and were 50 percent more likely to deliver by caesarean. The most alarming figures came from severe cases, where both preterm birth and preeclampsia — a condition involving dangerously high blood pressure in the second trimester — occurred at four times the rate seen in mild infections. Researchers suspect the virus triggers an inflammatory response that damages blood vessels and disrupts placental function, though the precise mechanism is not yet understood.
Not all experts received the findings without reservation. Dr. Deborah Money, who leads Canada's national pregnancy surveillance project, acknowledged the study's significance while questioning its methodology. She noted that it combined confirmed and suspected cases and drew heavily from countries like Mexico and South America, where healthcare access and social conditions differ sharply from Canada. Her own national dataset — built from 1,800 domestic cases — has confirmed higher hospitalization and preterm birth rates, but has not yet shown a statistically significant increase in stillbirths.
Despite those caveats, the weight of evidence has been enough to shift guidance. Money urged pregnant women to get vaccinated and take precautions against exposure, while also stressing that pandemic anxiety should not become a reason to skip prenatal appointments. Conditions like preeclampsia can only be detected through regular monitoring, and the clinics providing that care have put protective measures in place. Her message was direct: stay connected to your healthcare providers, take the precautions available to you, and do not let fear stand between you and the care that protects both you and your child.
Researchers at the University of Montreal have completed a sweeping analysis of pregnancy outcomes during the pandemic, and the findings are sobering: women who contract COVID-19 face measurably higher risks of stillbirth, preterm delivery, and a dangerous spike in blood pressure during pregnancy. The study, published Friday in the Canadian Medical Association Journal, synthesized data from 42 separate studies tracking 438,548 pregnant people worldwide.
Dr. Nathalie Auger and her team found that the severity of infection matters enormously. Women with symptomatic COVID-19 faced double the risk of preterm birth compared to those who carried the virus without symptoms. They were also 50 percent more likely to require a caesarean delivery. But the most striking finding concerned severe cases: pregnant women with serious COVID-19 infections showed a fourfold increase in both preterm birth and preeclampsia—a condition marked by dangerously elevated blood pressure in the second trimester—compared to those with mild disease.
The mechanism remains unclear, though researchers suspect the virus triggers an inflammatory cascade that damages blood vessels and disrupts placental function. The study's authors were direct in their conclusion: clinicians need to understand these risks and deploy preventive strategies to protect both mother and fetus. The research also underscores a gap in knowledge that has left obstetricians and neonatologists scrambling for guidance on how to counsel and manage pregnant patients during the pandemic.
Dr. Deborah Money, an obstetrician leading Canada's national surveillance project on pregnancy during COVID-19, offered a measured response. She noted that Canadian data so far—drawn from 1,800 cases tracked domestically—has confirmed higher hospitalization and preterm birth rates but has not yet shown a statistically significant increase in stillbirths. Money raised concerns about the Montreal study's methodology, pointing out that it lumped together women with confirmed infections and those with suspected cases, and that it drew from international research conducted in regions with vastly different access to prenatal care. She noted that some of the most troubling findings have come from Mexico and South America, where she suspects social determinants and healthcare access play a larger role than the virus itself.
Still, the evidence is accumulating. Canadian data has already documented that pregnant women with COVID-19 face higher hospitalization risk and preterm birth. The question of stillbirth remains open, but the pattern is clear enough that public health guidance has shifted. Money emphasized that pregnant women should get vaccinated and maintain precautions to limit exposure. At the same time, she stressed that fear of the pandemic should not keep women away from essential prenatal care. Clinics and hospitals are implementing protective measures, and conditions like high blood pressure—which might signal preeclampsia—can only be caught through regular monitoring. The message, she said, is simple: stay engaged with your healthcare providers, take precautions, and do not let pandemic anxiety prevent you from the care you need.
Notable Quotes
Symptomatic or severe COVID-19 is associated with a considerable risk of preeclampsia, preterm birth and low birth weight— Dr. Nathalie Auger, University of Montreal School of Public Health
It's very important that women access health care as needed. And don't be frightened of doing that because the pandemic is ongoing— Dr. Deborah Money, obstetrician and University of British Columbia professor
The Hearth Conversation Another angle on the story
Why does severity matter so much? Is the virus itself more damaging in severe cases, or is it something about how the body responds?
The researchers think it's the inflammatory response—the body's immune system overreacting to the virus in ways that damage blood vessels and the placenta. A mild infection might trigger a measured response, but severe COVID-19 sets off a cascade that affects the whole vascular system, which is critical during pregnancy.
The study looked at 438,000 pregnancies. That's a huge number. Why would Dr. Money say to take it with a grain of salt?
Because it's a meta-analysis—it's stitching together 42 different studies from different countries with different healthcare systems. Some of those studies included women who only suspected they had COVID, not confirmed cases. And in places with poor prenatal care access, the baseline risks are already higher. Money is saying the Montreal findings might be picking up those confounding factors, not just the virus.
So the Canadian data is different from what the Montreal study found?
Yes. Canada's tracked 1,800 cases and confirmed higher hospitalization and preterm birth. But they haven't seen the same spike in stillbirths that the meta-analysis suggests. Money is watching carefully, but she's not convinced the international data tells the whole story about what's happening in Canada specifically.
What should a pregnant woman actually do with this information?
Get vaccinated. Limit unnecessary exposure. Keep going to prenatal appointments—don't let fear keep you away from clinics. The virus is real and the risks are real, but so is the risk of missing a diagnosis like preeclampsia because you avoided care.
Is there a sense that this is still being figured out in real time?
Absolutely. Obstetricians are still learning. They're scanning every case, looking for patterns they didn't expect. The research is moving fast, but it's also incomplete. That's why Money keeps emphasizing that women need to stay connected to their doctors—so doctors can catch problems early.