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/m(2). If BMI <22.5 kg/m(2) and WC <78.5 cm were used as the reference, BMI between 22.5 and <24.0 kg/m(2) (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/m(2) 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/m(2) 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.