(HealthDay News) — An HbA1c threshold of 5.9% or greater can identify all women with gestational diabetes in early pregnancy, according to a study published online in Diabetes Care.

Ruth C.E. Hughes, MBBCh, from the University of Otago in New Zealand, and colleagues analyzed data from a group of women who completed an early oral glucose tolerance test (OGTT) and HbA1c tests. Pregnancy outcome data were also assessed.

In 16,122 women, HbA1c was measured at a median of 47 days’ gestation. Twenty-three percent of those offered (n=974) took an early OGTT, and in this subset all 15 cases of diabetes were identified with HbA1c ≥5.9%. For gestational diabetes before 20 weeks, this threshold was 98.4% specific (positive predictive value, 52.9%). 

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Excluding the women referred for gestational diabetes, women with HbA1c of 5.9% to 6.4% had poorer pregnancy outcomes than those with HbA1c <5.9% (n=8,174): relative risk of major congenital anomaly was 2.67; preeclampsia, 2.42; shoulder dystocia, 2.47; and perinatal death, 3.96.

“HbA1c measurements were readily performed in contrast to the low uptake of early OGTTs,” the researchers wrote.


  1. Hughes RCE et al. Diabetes Care. 2014;doi:10.2337/dc14-1312.