Relationship of Early Pregnancy Waist-to-Hip Ratio versus Body Mass Index with Gestational Diabetes Mellitus and Insulin Resistance

Objective To determine the risk of gestational diabetes mellitus (GDM) and insulin resistance (IR) in obesity defined by body mass index (BMI), waist-to-hip ratio (WHR), or both combined. Methods Secondary analysis of a randomized multicenter trial of antioxidant supplementation versus placebo in nulliparous low-risk women to prevent pregnancy associated hypertension. Women between 9 and 16 weeks with data for WHR and BMI were analyzed for GDM (n = 2,300). Those with fasting glucose and insulin between 22 and 26 weeks (n = 717) were analyzed for IR by homeostatic model assessment of IR (normal, <= 75th percentile). WHR and BMI were categorized as normal (WHR, < 0.80; BMI, < 25 kg/m(2)); overweight (WHR, 0.8-0.84; BMI, 25-29.9 kg/ m(2)); and obese (WHR, >= 0.85; BMI >= 30 kg/m(2)). Receiver operating characteristic curves and logistic regression models were used. Results Compared with normal, the risks of GDM or IR were higher in obese by BMI or WHR. The subgroup with obesity by WHR but not by BMI had no increased risk of GDM. BMI was a better predictor of IR (area under the curve [AUC]: 0.71 [BMI], 0.65 [WHR], p = 0.03) but similar to WHR for GDM (AUC: 0.68 [BMI], 0.63 [WHR], p = 0.18). Conclusion Increased WHR and BMI in early pregnancy are associated with IR and GDM. BMI is a better predictor of IR compared with WHR. Adding WHR to BMI does not improve its ability to detect GDM or IR.