Interactions between general and central obesity in predicting gestational diabetes mellitus in Chinese pregnant women: A prospective population‐based study in Tianjin, China

Background The aim of the present study was to define cut‐off points of body mass index (BMI) and waist circumference (WC) for gestational diabetes mellitus (GDM) and to investigate any interactions between high BMI and high WC on the risk of GDM in pregnant Chinese women. Methods From 2010 to 2012, 17 803 women in Tianjin, China, who were at 4–12 weeks gestation were recruited to the study. Gestational diabetes mellitus was diagnosed according to the criteria of the International Association of Diabetes and Pregnancy Study Group at 24–28 weeks gestation. Binary logistic regression was used to obtain odds ratios (ORs) and 95% confidence intervals (CIs) while controlling for the confounding effects of traditional risk factors. Restricted cubic spline was used to identify cut‐off points of WC and BMI, if any, for GDM. Results Gestational diabetes mellitus developed in 1383 (7.8%) women. The risk of GDM increased steeply with increasing WC from ≥78.5 cm and BMI ≥22.5 kg/m2. If BMI <22.5 kg/m2 and WC <78.5 cm were used as the reference, BMI between ≥22.5 and <24.0 kg/m2 (multivariable OR 1.76; 95%CI 1.47–2.10) and WC between ≥78.5 and <85.0 cm (multivariable OR 1.53; 95%CI 1.31–1.78) were independently associated with increased risks of GDM. In addition, the presence of both BMI ≥22.5 kg/m2 and WC ≥78.5 cm further increased the OR to 2.83 (95% CI 2.44–3.28), with significant additive interaction. Conclusions Body mass index ≥22.5 kg/m2 and WC ≥78.5 cm measured up to 12 weeks of gestation were independently and synergistically associated with increased risks of GDM in Chinese pregnant women.