ABSTRACT: In 2010, the International Association of the Diabetes and Pregnancy Study Groups (IADPSG) recommended a new strategy for the screening and diagnosis of gestational diabetes mellitus (GDM). However, no study has indicated that adopting the IADPSG recommendations improves perinatal outcomes. The objective of this study was to evaluate the effects of implementing the IADPSG criteria for diagnosing GDM on maternal and neonatal outcomes.Previously, we used a two-step approach (a 1-h, 50-g glucose challenge test followed by a 3-h, 100-g glucose tolerance test when indicated) to screen for and diagnose GDM. In July 2011, we adopted the IADPSG recommendations in our routine obstetric care. In this study, we retrospectively compared the rates of various maternal and neonatal outcomes in all women who delivered after 24 weeks of gestation during the periods before (P1, between January 1, 2009 and December 31, 2010) and after (P2, between January 1, 2012 and December 31, 2013) the IADPSG criteria were implemented. Pregnancies complicated by multiple gestations, fetal chromosomal or structural anomalies, and pre-pregnancy diabetes mellitus were excluded. Our results showed that the incidence of GDM increased from 4.6% using the two-step method to 12.4% using the IADPSG criteria. Compared to the women in P1, the women in P2 experienced less weight gain during pregnancy, lower birth weights, shorter labor courses, and lower rates of macrosomia (<4000 g) and large-for-gestational age (LGA) infants. P2 was a significant independent factor against macrosomia (adjusted odds ratio [OR] 0.63, 95% confidence interval [CI] 0.43-0.90) and LGA (adjusted OR 0.74, 95% CI 0.61-0.89) after multivariable logistic regression analysis.The adoption of the IADPSG criteria for diagnosis of GDM was associated with significant reductions in maternal weight gain during pregnancy, birth weights, and the rates of macrosomia and LGA.