Prepregnancy body mass index and other risk factors for early-onset and late-onset haemolysis, elevated liver enzymes and low platelets (HELLP) syndrome: a population-based retrospective cohort study in British Columbia, Canada

Background Obesity increases risk of pre-eclampsia, but the association with haemolysis, elevated liver enzymes and low platelets (HELLP) syndrome is understudied.Objective To examine the association between prepregnancy body mass index (BMI) and HELLP syndrome, including early-onset versus late-onset disease.Study design A retrospective cohort study using population-based data.Setting British Columbia, Canada, 2008/2009–2019/2020.Population All pregnancies resulting in live births or stillbirths at ≥20 weeks’ gestation.Methods BMI categories (kg/m2) included underweight (