Unveiling Hidden Risks: The CMAJ Study on Postpartum Complications in Canada

A groundbreaking study published in the Canadian Medical Association Journal (CMAJ) on March 16, 2026, has shed light on a critical gap in maternal health monitoring across Canada. Titled "Severe maternal morbidity from conception to 6 weeks postpartum in Ontario: a population-based, longitudinal cohort study," the research analyzed over 1.09 million births in Ontario between 2012 and 2021. Led by researchers from McMaster University, St. Michael's Hospital, and the Institute for Clinical Evaluative Sciences (ICES), it reveals that nearly 30 percent of life-threatening complications occur in the postpartum period—up to six weeks after delivery—a time when traditional surveillance often falls short.

Severe maternal morbidity (SMM) encompasses conditions like major hemorrhage, sepsis, acute organ dysfunction, and eclampsia that pose immediate threats to life. The study found an overall SMM rate of 27.24 cases per 1,000 births, affecting approximately 29,832 pregnancies. While 55 percent of cases happened during labor and delivery (intrapartum), 16 percent occurred before admission for birth (antepartum), and a striking 29 percent emerged postpartum. This distribution underscores how focusing solely on the delivery room misses about 45 percent of events.

McMaster University epidemiologist Giulia Muraca, senior author, emphasized the need for broader tracking: "If we can better surveil when and in whom these cases are occurring, we can do a better job of responding to those patterns and reducing the number." This research, part of the SERENE Project funded by the Juravinski Research Institute, highlights Canadian universities' pivotal role in advancing public health through data-driven insights.

What Constitutes Severe Maternal Morbidity?

Severe maternal morbidity refers to a cluster of unexpected outcomes from obstetric interventions or complications that nearly result in death or cause significant short- or long-term health issues. In clinical terms, it includes indicators such as severe preeclampsia/HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), major postpartum hemorrhage exceeding 1,500 mL blood loss, sepsis defined by organ dysfunction due to infection, acute kidney injury, and the need for mechanical ventilation or hysterectomy.

The CMAJ study used validated algorithms from ICES databases, linking birth records, hospital admissions, and emergency visits to capture these events comprehensively. For context, severe hemorrhage topped the list overall at 6.10 per 1,000 births, but patterns shifted by period: acute abdomen dominated antepartum cases (1.94 per 1,000), hemorrhage intrapartum (5.28 per 1,000), and sepsis postpartum (4.69 per 1,000). These definitions align with World Health Organization near-miss criteria, emphasizing life-threatening conditions rather than just mortality.

Understanding SMM is crucial because it often precedes maternal death. In Ontario, a coroner's review showed 47 percent of maternal deaths occur antepartum and 46 percent postpartum, with only 8 percent intrapartum—mirroring the study's morbidity patterns.

Timing Matters: When Do Complications Strike?

The study's temporal breakdown is eye-opening. Antepartum SMM (4.39 per 1,000 births) often involves non-obstetric issues like appendicitis leading to peritonitis or preterm labor. Intrapartum events (15.46 per 1,000) peak with hemorrhage and preeclampsia during active labor. But postpartum SMM (8.25 per 1,000) surges due to infections like sepsis, which accounted for nearly half of these cases.

Over 40 percent of postpartum cases presented via emergency departments, indicating many women sought care outside routine obstetric channels. Trends from 2012 to 2021 showed a slight rise in overall SMM (from 26.01 to 27.32 per 1,000), with increases in acute renal failure and hysterectomies, though surgical complications declined.

This timeline challenges the status quo, where monitoring typically ends at hospital discharge. As co-author Rohan D’Souza from McMaster noted, expanding surveillance could prevent escalation, especially since SMM impacts long-term health, fertility, and mental well-being.

Risk Factors: Who Faces the Greatest Threats?

The research identified clear demographic and clinical vulnerabilities. Nulliparous women (first pregnancy) faced heightened risks across periods, with odds ratios (OR) of 1.69 intrapartum. Age played a U-shaped role: teens under 20 had double the antepartum risk (OR 2.22), while those over 40 doubled intrapartum odds (OR 2.11).

Comorbidities amplified dangers—Type 1 diabetes showed ORs up to 6.19 antepartum. Multiple gestations tripled intrapartum risk (OR 3.80), and Black maternal race consistently elevated odds (OR 1.52 overall). Socioeconomic factors mattered: lowest income quintile increased risk by 26 percent intrapartum, and rural residents by 29 percent. Substance exposure and assault history further compounded vulnerabilities (ORs 2.46 and 2.64 antepartum).

• High-risk groups: Younger/older mothers, Black women, low-income/rural residents, those with diabetes, multiples, or substance use.
• Protective factors: Higher parity (after first birth), urban access, no comorbidities.

These inequities call for targeted university-led interventions, like community health programs at institutions such as the University of Toronto or UBC.

The Postpartum Blind Spot: Sepsis and Hemorrhage in Focus

Postpartum sepsis emerged as the dominant threat, comprising 49 percent of cases and often stemming from uterine infections or wound issues post-C-section. Severe hemorrhage, though less common postpartum (0.75 per 1,000), remains deadly if untreated. Real-world examples abound: CBC reported cases like Paige Eaton's post-C-section sepsis, requiring ICU stays despite follow-ups.

Canada's maternal mortality ratio hovers around 11 per 100,000 live births (WHO data), higher than peers like Japan, with postpartum hemorrhage a leading cause. Yet, only a six-week checkup is standard in Ontario, amid primary care shortages—1 in 5 lack a family doctor.

The full CMAJ study details how 3.32 percent of cases spanned periods, urging holistic care.

Why Traditional Monitoring Misses the Mark

Current Canadian protocols emphasize intrapartum surveillance, per Public Health Agency guidelines, but overlook outpatient postpartum risks. Emergency visits spike postpartum (40 percent of SMM), yet symptoms like fever or bleeding are often dismissed. Postpartum depression affects 8-15 percent, masking physical red flags.

Global comparisons: U.S. studies show similar postpartum burdens, but Canada's universal care should enable better tracking. The Society of Obstetricians and Gynaecologists of Canada (SOGC) stresses continuity, yet implementation lags.

Canadian Maternal Health in Broader Context

Canada boasts robust maternity care—97 percent of pregnancies uneventful—but SMM rates (under 18 per 1,000 intrapartum-only) underestimate true burden. Maternal deaths rose slightly post-COVID, per Statistics Canada. Provinces vary: Ontario's data proxies national trends, but rural Atlantic Canada faces access gaps.

Comparisons: Australia's postpartum monitoring includes home visits; UK's NICE guidelines mandate week-one checks. Canada's Family-Centred Maternity Care (2023) advocates personalized plans, but uptake is uneven.

Public Health Agency postpartum guidelines outline screening, yet the CMAJ study pushes for tech like remote BP monitors.

Voices from the Research Frontlines

Senior author Giulia Muraca (McMaster) calls for a "whole-system approach" integrating ERs, primary care, and midwifery. SOGC's Jocelynn Cook links SMM to deaths: "Understanding patterns prevents tragedies." UBC's Sarka Lisonkova advocates risk assessments pre-discharge.

Patient advocates like those from Postpartum Support International highlight dismissed symptoms. University researchers, via ICES' linked data expertise, exemplify how academic collaboration drives policy.

Pathways to Prevention: Recommendations and Innovations

The study proposes a Canadian Obstetric Surveillance System (CanOSS) for national tracking. Actionable steps:

• Extend monitoring to 42 days postpartum with home visits or apps for high-risk cases.
• Train non-obstetric providers on SMM signs.
• Equity initiatives: Culturally safe care for Black/Indigenous women, substance support.
• Inter-professional models: Midwives/public health nurses for follow-ups.

Pilots like BC's Perinatal Services pathways show promise. Universities like McMaster train future OBGYNs in these protocols.

McMaster's press release details SERENE's lived-experience input.

The Academic Backbone: Universities Driving Change

Canadian higher education fuels this progress. McMaster's Population Health Research Institute, ICES (UofT-affiliated), and St. Michael's integrate big data with clinical care. Funding from CIHR supports such cohorts, training PhDs in epidemiology.

Implications for academia: More grants for maternal health, interdisciplinary programs blending data science and obstetrics. Institutions like UBC and UofT lead global trials, positioning Canada as a research hub.

Photo by Chelsey Faucher on Unsplash

Looking Ahead: Trends, Challenges, and Hope

SMM rose modestly over a decade, tied to comorbidities like obesity/diabetes. Climate impacts, aging mothers, and pandemics loom. Yet, declining ventilation needs signal progress. Optimism lies in tech: Wearables for vital signs, AI risk prediction. Policy shifts could halve preventable cases, saving lives and costs (SMM hospitalizations exceed $1B annually). As Muraca concludes, expanded surveillance is key. Canadian universities stand ready to lead, fostering researchers who turn data into safer births.

For those in health research, opportunities abound to contribute. Explore roles advancing maternal safety.