22 OCTOBER · PEER-REVIEWED COHORT STUDY
Pregnancy weight gain and serious maternal complications
Clinical question and result. Is weight gain during pregnancy associated with severe maternal illness across different pre-pregnancy BMI groups? In more than 1.03 million singleton pregnancies in Ontario, excessive gain was associated with a higher rate of severe maternal morbidity in every BMI category. Inadequate gain was also associated with higher risk among women in the normal-weight and overweight groups. The absolute differences were modest: severe morbidity occurred in 12.18 per 1,000 births with guideline-range gain, 14.08 with inadequate gain and 16.09 with excessive gain.
Evidence strength and limitations. The study was very large and used linked birth and hospital records, but it was retrospective and cannot prove that weight gain caused the complications. Fluid retention from pre-eclampsia may partly explain higher late-pregnancy weight, and the composite outcome combined conditions with different causes. Canadian findings may not transfer directly to South African populations or resources.
Practical implication. Record pre-pregnancy weight or early BMI where possible and discuss a realistic weight-gain range without stigma. Review nutrition, blood pressure, diabetes risk and other medical conditions together. Do not turn the study’s estimated lowest-risk values into new targets or encourage weight loss during pregnancy without specialist guidance.
Verdict: Practice remains unchanged—continue local pregnancy guidance, but make weight monitoring and individualised counselling more consistent.
Read the JAMA Network Open study →