Pregnancy weight gain above guidelines raises severe complication risk
Researchers examined more than one million Ontario births and found that gaining more weight than recommended during pregnancy was tied to a higher risk of severe maternal complications. The association held across all starting BMI groups, and pre-existing conditions such as diabetes or high blood pressure roughly doubled the risk. The study appears in JAMA Network Open.
The analysis drew on BORN Ontario records for over one million pregnancies. Just over half exceeded recommended gestational weight gain, while nearly one-fifth fell below it; researchers identified more than 15,000 cases of severe maternal morbidity.
Higher-than-recommended gain was associated with elevated risk in every starting BMI category. Diabetes, asthma, or hypertension before pregnancy roughly doubled the likelihood of severe complications, and risks rose further when gain was outside recommendations; below-recommended gain also carried higher risk in some BMI groups.
This finding could influence how clinicians discuss pregnancy weight with patients and may prompt broader prenatal support strategies. Because more than half of pregnancies exceeded recommendations, the impact may extend across BMI groups, not only those with higher starting weight. People with diabetes, asthma, or hypertension may face compounded risks, making tailored monitoring and accessible lifestyle support potentially important. Population-level changes could affect maternity care resources and workplace or community health programs, though individual counseling alone may be insufficient.