Background: Pregnancy complicated by Gestational Diabetes Mellitus(GDM) is associated with adverse maternal and neonatal outcomes. A 1-hour glucose level (1-hrBGL) ≥10mmol/L on a 75g oral Glucose Tolerance Test (oGTT) is included in the new International Association Diagnostic Pregnancy Study Groups (IADPSG) GDM diagnostic criteria (1).

Aim: To explore whether a diagnosis of GDM according to a 1-hrBGL ≥10mmol/L on an oGTT conferred an increased risk of adverse outcomes in our patient cohort.

Methods: We analysed de-identified prospectively collected data (2009-2013), from women diagnosed with a 1-hrBGL ≥10mmol/L only, compared to those diagnosed on fasting or 2-hour glucose levels, (or both), according ADIPS(1998) Australian criteria, or on a glucose challenge test of >11.0mmol/L. Outcomes analysed included: rates of insulin therapy, premature delivery, caesarean delivery, small for gestational age(SGA), large for gestational age(LGA) infant and abnormal post-partum oGTT. Independent samples t-tests and chi-square analyses were used to test for statistical significance (p<0.05).

Results: There were 1786 complete records, 94 of whom were treated for GDM exclusively on the basis of an elevated 1-hrBGL on oGTT. There were no demonstrated differences in baseline characteristics of age, gravida, parity, pre-pregnancy BMI, risk factors for GDM, oGTT parameters, HbA1c, pregnancy weight gain, or maximum dose of insulin use between those diagnosed and those not diagnosed on 1-hrBGL only. In women diagnosed on 1-hrBGL, compared to the other groups, there was no difference in caesarean delivery or SGA infants, a trend to lower LGA rates (p=0.09), and significantly lower rates of insulin therapy, premature delivery and abnormal post-partum OGTT (Table 1).

Conclusion: Women diagnosed with GDM on 1-hrBGL criterion alone appeared to have lower rates of adverse outcomes with significantly lower rates of insulin use, premature delivery and abnormal oGTT post-partum. There was a trend to lower LGA rates.