Excessive Weight Gain Linked to Maternal Risk
More than half of all pregnancies—approximately 53%—exceed the weight gain guidelines established by the Institute of Medicine. A study published October 22 in JAMA Network Open links this excessive gestational weight gain to a heightened risk for severe maternal morbidity (SMM) across every prepregnancy body mass index (BMI) category.
Tracking Over One Million Deliveries
The retrospective cohort study, led by Sahar Khademioore of McMaster University in Hamilton, Ontario, analyzed more than 1 million singleton hospital deliveries spanning 2012 to 2022. During these hospitalizations, the overall rate of SMM reached 14.59 per 1,000 births.
The data reveals a clear correlation: individuals who gained excessive weight faced higher SMM risks than those with adequate gain, with adjusted risk ratios ranging from 1.16 to 1.33. While inadequate weight gain also increased risk, this effect was limited to those in the normal weight and overweight BMI categories.
The Role of Preexisting Health Factors
Clinical history serves as a critical indicator for patient outcomes. A preexisting medical condition is associated with an approximate twofold increase in the risk for SMM among patients who otherwise achieved adequate gestational weight gain. The highest risk levels occur when a patient presents with both a preexisting condition and either inadequate or excessive weight gain.
A Shift Toward Risk-Stratified Counseling
The findings suggest that current categorical targets, which treat all individuals within a BMI class as equivalent, may be insufficient. The authors advocate for risk-stratified counseling that integrates an individual’s specific BMI subclass with their unique medical comorbidities.
Researchers noted limitations in the study’s scope, as SMM data was restricted to the delivery hospital stay. Complications occurring before or after that specific admission were not captured. The study grouped 13 different clinical indicators into a single composite outcome, a method that may mask variations in the underlying mechanisms of these health events.
Excessive Weight Gain Increases Severe Maternal Morbidity Risk
The composite outcome used to define SMM includes 13 relevant clinical indicators recorded during delivery. While the study found excessive weight gain consistently linked to higher risk, the association with inadequate weight gain remained statistically significant only for those in the normal weight and overweight categories. Because few events were reported in individuals classified within obesity classes II and III, the findings for those specific groups may lack the precision of other cohorts.
Ultimately, these results suggest that pregnancy weight management must move beyond broad targets to a more personalized approach that accounts for a patient’s medical history and specific BMI subclass.