Comparison of the performance of screening test for gestational diabetes in singleton versus twin pregnancies

OBJECTIVE: We compared the performance of the 50-g glucose challenge test (GCT) in singleton versus twin pregnancies and investigated the need for adjusting GCT cutoff values for gestational diabetes mellitus (GDM) in twin pregnancies among Korean women. METHODS: A retrospective chart review was performed in women who underwent GCT at 24 to 28 weeks' gestation and delivered in our department between January 2000 and April 2008. GCT performance was compared between singleton and twin pregnancies for an ideal cutoff value of the GCT for GDM screening. RESULTS: GCT results were available in 3,578 pregnancies (3,435 singleton and 143 twin pregnancies). The mean GCT value was higher in the twin group than in the singleton group. Women in the twin group had a higher mean GCT value (P=0.043) and a higher incidence of GCT ≥130, ≥135, and ≥140 mg/dL (P=0.014, 0.005, and 0.015, respectively). The false positive rate for GCT ≥140 mg/dL was significantly higher in the twin than in the singleton group (P=0.042). The optimal GCT screening cutoff value appears to be ≥145 mg/dL in twin pregnancies. CONCLUSION: Our study demonstrates that the GCT is associated with a higher false positive rate in twin rather than singleton pregnancies. This study suggests we should consider adjusting the GCT cutoff value for GDM in Korean twin pregnancies.