One-step versus two-step diagnostic testing for gestational diabetes: a randomized controlled trial.

Objective: To evaluate the incidence of gestational diabetes mellitus (GDM) using the one-step as compared with the two-step approach. Study design: This was a parallel group nonblinded randomized trial conducted at Thomas Jefferson University Hospital (TJUH) in Philadelphia, Pennsylvania from June 2016 to December 2016. The primary outcome was GDM incidence in the one-step compared to the two-approach. Pregnant women without a history of pregestational diabetes were offered screening for GDM at gestational age 24-28 weeks. Obese women, defined as having a BMI ≥30 kg/m2 , as well as those with a history of a pregnancy complicated by GDM, a history of a macrosomic baby (>4000 g), or with polycystic ovarian syndrome (PCOS), were offered early screening at their initial prenatal visit, and screening was repeated at 24-28 weeks if initially normal. Women were excluded if they had pre-existing diabetes or had a history of bariatric surgery. Women who were eligible were randomized in a 1:1 ratio to either the one-step or two-step approaches. A sample size of 142 women was planned per group. Women randomized to the one-step approach, after an overnight fast, were given a 2-h glucose tolerance test, which consisted of a 75-g glucose load. Blood glucose levels were measured fasting, at 1 h and 2 h after the glucose load. Diagnostic cutoffs for GDM diagnosis were one value of either fasting ≥92 mg/dL, 1 h ≥180 mg/dL, or 2 h ≥153 mg/dL, respectively. Women randomized to the two-step approach were given a nonfasting 50-g glucose load, and the blood glucose level was measured an hour after the glucose load. If that value was ≥135 mg/dL, the patient had a 3-h glucose tolerance test consisting of a 100-g glucose load. Diagnostic cutoffs for GDM diagnosis for this 3-h test were ≥2 abnormal values of fasting ≥95 mg/dL, 1 h ≥180 mg/dL, 2 h ≥155 mg/dL and 3 h ≥140 mg/dL, respectively. All analyses were done using an intention-to-treat approach, evaluating women according to the treatment group to which they were randomly allocated. Results: Two hundred eighty-four women agreed to take part in the study and underwent randomization from June 2015 to December 2015. Of them, 249 completed the screening and were followed up for the primary endpoint. Out of the 249 women who completed the screening, 123 were assigned to the one-step group and 126 to the two-step group. GDM occurred in 10 women (8.1%) in the one-step group, and 7 women (5.6%) in the two-step group ( p  = .42). Preeclampsia, preterm birth (PTB), induction of labor, mode of delivery and incidence of gestational age (OASIS) were not significantly different. Perinatal outcomes were similar as well. Conclusions: Screening for GDM with one-step, compared with the two-step approach, resulted in a similar incidence of GDM.