Excess Pregnancy Weight Gain Linked to Severe Maternal Complications
Excessive weight gain during pregnancy may increase the risk of severe, life-threatening health complications, according to a large-scale study published in JAMA Network Open. Researchers at McMaster University found that putting on more weight than current clinical guidelines recommend was associated with serious maternal morbidity—unforeseen conditions that can cause significant harm or danger to a pregnant woman.
The study analyzed more than one million births recorded across Ontario between 2012 and 2022 using health data from the Better Outcomes Registry & Network (BORN) Ontario. Out of all the pregnancies examined in the dataset, nearly 53 percent of the women exceeded the recommended gestational weight gain limits.
Independent Risks Across Different Body Mass Indexes
The elevated health risks persist regardless of a woman’s pre-pregnancy body mass index (BMI) or starting weight. Clinical guidelines for gestational weight gain differ depending on early-pregnancy BMI measurements, with physicians typically advising women with higher BMIs to gain less weight than those with lower baseline measurements.
Underlying Health Conditions Double the Threat
Weight alone does not account for every adverse outcome observed in the clinical data. The study demonstrates that the risk of severe maternal health complications is even higher—about double—among women who manage pre-existing health conditions such as hypertension, asthma, or diabetes.
In certain instances, elevated risks of severe health complications also appeared among women who gained less weight than the recommended clinical thresholds, including those carrying pre-existing medical conditions.
Clinical Perspectives on Maternal Support
Kaberi Dasgupta, a senior scientist and professor of medicine at McGill University who was not involved in the research, noted that the findings highlight the problem related to weight gain and the need to provide support to pregnant women.
“Pregnancy is a crucial period for understanding future risks for mothers and babies, but also current risks,” Dasgupta said in a video interview. “It is very important to understand the role of weight gain during pregnancy, because that reinforces the importance placed on this issue for pregnant women, their families, their health-care professionals, and society.”
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