To evaluate the prevalence and clinical outcomes using a one-step method versus a two-step method to screen gestational diabetes mellitus.

Objective: The goal of this study is to compare the prevalence and clinical outcomes of a one-step with a two-step screening method, both of which are commonly used for the diagnosis of gestational diabetes mellitus (GDM).

Methods: Women who presented for GDM screening and who consented to participate in this study were randomized into two groups. The women in Group 1 (n = 386) were screened using a one-step method (2-h, 75 g oral glucose tolerance test (OGTT)) and in Group 2 (n = 400) by a two-step method (the 50 g glucose challenge test (GCT) followed by the 100 g OGTT). The pregnancies were then classified into three subgroups as follows: women who had negative 2-h 75 g OGTT results according to IADPSG criteria (IADPSG-negative), women with negative 50 g GCT results (GCT-negative) and women with positive 50 g GCT results but negative 3-h 100 g OGTT results according to C&C criteria (C&C-negative).

Results: The prevalence of GDM using the one-step and two-step methods was 14.5% and 6%, respectively. In adjusted multivariable regression models, women in the GCT-negative and the C&C-negative groups had greater risk of polyhydramnios than women in the IADPSG-negative group [adjusted prevalence risk ratios (aPR), 1.40; 95% confidence intervals (CI), 1.03-1.91; aPR, 2.76; 95% CI, 1.27-6.02, respectively]. Women in the C&C-negative group had greater risk of pre-eclampsia than women in the IADPSG-negative group (aPR, 3.30; 95% CI, 1.57-6.91).

Conclusions: Women who were defined as having normal glucose tolerance by IADPSG had better perinatal outcomes than women who were defined as having normal glucose tolerance by GCT and women who were GCT-positive with a negative OGTT.