Optimal maternal neck and waist circumference cutoff values for prediction of gestational diabetes mellitus at the first trimester in Turkish population; a prospective cohort study.

To investigate if the maternal neck (NC) and waist (WC) circumferences measured in the first trimester of pregnancy have a predictive value in diagnosing gestational diabetes mellitus (GDM). In this prospective study NC and WC of pregnant women were measured at 11-14th weeks. GDM was evaluated with a two-step oral glucose tolerance test at 24-28th weeks. A total of 525 women were recruited; 49(9%) developed GDM. NC was positively correlated with WC (: 0.583,  < .001), BMI (: 0.533,  < .001), age (: 0.123,  = .002), parity (: 0.170,  < .001), and 50 g OGTT levels (: 0.206,  < .001). Regarding the area under receiver operating characteristic (ROC) curve (AUC) analysis of NC and WC for predicting GDM were 0.585 (95% confidence interval (CI): 0.50-0.66,  = .043), and 0.693 (95%CI: 0.61-0.76,  < .001). The optimal cut off level of maternal NC was >38.5 cm, with 69% sensitivity and 45% specificity, and WC was >84.50 cm with a sensitivity of 78% and a specificity of 54%. Increased WC >84.50 cm (OR: 3.58, 95% CI:1.77-7.27;  < .001) and age >25 (OR: 3.05, 95% CI:1.38-6.72;  = .006) were independent predictors for the development of GDM adjusted for age, gravidity, parity, BMI, and NC. Maternal NC and WC were significantly higher in women with GDM; however, only maternal WC was a significant predictive marker for GDM in low-risk pregnant women.