Obesity in Pregnancy

Maternal obesity is defined by a pre-pregnancy body mass index (BMI) of 30 kg/m² or greater. Canadian adult BMI categories are underweight (<18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (≥30 kg/m²). Use the pre-pregnancy or earliest reliable pregnancy weight for classification; later gestational weight gain should not change the baseline category. BMI is a risk marker, not a diagnosis of gestational diabetes, pre-eclampsia, fetal overgrowth, or fetal compromise. Adipose-related insulin resistance and vascular inflammation increase metabolic and hypertensive risk, while pregnancy’s normal hypercoagulable state adds to venous stasis and VTE risk. The same body habitus can also make fetal assessment, airway management, and neuraxial anaesthesia more technically difficult. The practical approach is not weight loss during pregnancy. It is respectful, individualized care: identify complications early, support appropriate gestational gain, anticipate assessment and delivery challenges, and reduce preventable postpartum VTE risk.