By extending the postpartum surveillance period to 6 weeks after delivery, researchers found that 40% of cases of severe maternal morbidity (SMM) occurred outside of the traditional monitoring window in Ontario, Canada, according to a new study.

SMM affected nearly 3% of pregnancies between conception and 6 weeks postpartum, the researchers found. These pregnancy-related complications can include serious issues such as severe bleeding, sepsis, or organ failure, which can lead to hospitalization, long-term disability, or death.

“Studying SMM provides a sensitive indicator of how well our maternity care system is functioning. Because SMM events are more common than maternal deaths, they allow us to identify patterns, gaps in care, and opportunities for prevention much earlier,” senior author Giulia Muraca, PhD, associate professor of obstetrics and gynecology at McMaster University and adjunct scientist at ICES in Hamilton, Ontario, told Medscape News Canada.

“The consequences of SMM extend far beyond the delivery room,” Muraca added. “Survivors can face long-term physical health problems, increased risk in future pregnancies, and significant mental health impacts such as anxiety, depression, or posttraumatic stress. These experiences affect not only the birthing person but also their infants, partners, and families.”

The study was published on March 16 in CMAJ.

Monitoring for Severe Postpartum Complications

Most surveillance studies in Canada monitor and report cases of SMM that occur during labor and delivery, or the intrapartum period, with estimates of about 18 SMM cases per 1000 births.

The investigators conducted a population-based cohort study of births at 20 or more weeks of gestation through 6 weeks postpartum, looking at administrative data in Ontario for 2012-2021. The research team assessed the frequency and types of SMM overall, including by period (antepartum, intrapartum, and 6 weeks postpartum).

Among nearly 1.1 million births, 27.2 per 1000 births involved an SMM event, or 2.7%, which was higher than the previous estimate of 1.8%. This means that nearly 10,000 pregnant patients in Canada experience severe maternal complications each year, Muraca said.

Among those events, 15.6% occurred antepartum, with 55% intrapartum and 29% postpartum. About 19% of pregnant people visited an emergency department, mostly during the antepartum and postpartum periods.

The most common SMM type overall was severe hemorrhage (6.1 per 1000 births), followed by severe preeclampsia and sepsis. Acute appendicitis (1.94 per 1000 births) was most common during the antepartum period, severe hemorrhage during the intrapartum period (5.28 per 1000 births), and sepsis during the postpartum period (4.69 per 1000 births).

Certain factors were associated with higher SMM risks, including age, maternal race, conception through assisted reproductive technology, labor induction, cesarean delivery, preexisting medical conditions, immigrant status, income, rural/remote residence, substance use during pregnancy, and assault. For instance, antepartum complications were highest in patients aged 15-19 years, while intrapartum and postpartum conditions were highest in patients aged 40-49 years. In addition, type 1 diabetes had the strongest association with antepartum SMM.

“Serious pregnancy complications don’t only happen in the delivery room,” said Muraca. “Improving maternal safety means strengthening care across the entire system: from early pregnancy to weeks after birth, including emergency departments, primary care, and postpartum follow-up.”

Expanding Research and Prevention

By expanding the surveillance window, researchers can capture serious complications that may occur before or after labor, which would align with the World Health Organization’s definition of maternal mortality and near-miss events, the researchers wrote. For instance, a recent analysis of coroner data in Ontario found that most maternal deaths occur during the antenatal (46.5%) and postpartum (45.8%) periods, with only 7.7% occurring during the intrapartum period.

“Historically, maternal health in populations was monitored using maternal death rates as the key indicator. The decline in maternal mortality over the last several decades has led to an increased emphasis on monitoring severe maternal morbidity,” K. S. Joseph, MD, PhD, professor of obstetrics and gynaecology at the University of British Columbia and investigator at BC Children’s Hospital in Vancouver, told Medscape News Canada.

Joseph, who wasn’t involved with this study, has researched maternal mortality and morbidity, including risk factors for severe preeclampsia and other disorders.

“Understanding the clinical and population health burden of SMM is the first step toward improving maternal health,” he said. “Information on the frequency of each SMM and its severity is critical for developing a rational clinical and population health strategy for making pregnancy safe and ensuring healthy mothers and babies.”

In future studies, researchers will need to look closely at SMM definitions, timing, and patient characteristics. For instance, some antepartum events could be linked to a nonobstetrical condition such as a pulmonary embolism or a surgical condition, Joel Ray, MD, professor of medicine at the University of Toronto and clinician-scientist at St. Michael’s Hospital in Toronto, told Medscape News Canada. Ray, who wasn’t involved with this study, has researched SMM and risk factors such as age.

“The methods described by the authors make it difficult to fully understand how they separated an antepartum SMM event from an intrapartum event,” he noted. “Their examination of the maternal racial groups should also be interpreted with great care.”

Broad categories such as “Asian” or “Black” can include women with extremely different risks for pregnancy-related complications, Ray noted. Women from the Philippines, for instance, tend to have higher rates of severe hypertension than women from China or Korea. Similarly, women from Eritrea or Ethiopia face different risks for preeclampsia than women from Jamaica or Ghana, he said.

Additional studies and prevention measures should focus on trends in other patient characteristics as well, including age-related risks, Isabelle Malhamé, MD, assistant professor of medicine at McGill University in Montreal, told Medscape News Canada. Malhamé, who wasn’t involved with this study, has written about the need for a Canadian Obstetric Survey System to monitor SMM trends.

“These trends reflect changes in the pregnant population, and care must adapt to these new pressing needs in maternal health,” she said. “Health service delivery must be interdisciplinary and evolve to account for complexity. Importantly, solutions must be cocreated with health service users, and they should support customized approaches to care.”

The study was supported by funds from the Juravinski Research Institute, in partnership with Hamilton Health Sciences, McMaster University, and St. Joseph’s Healthcare Hamilton, as part of the SERENE Project. Muraca reported receiving funding from the Juravinski Research Institute to her institution in support of the study. Joseph, Ray, and Malhamé reported having no relevant financial relationships.

Carolyn Crist is a health and medical journalist who reports on the latest studies for Medscape, MDedge, and WebMD.