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The Antepartum Glucose Values that Predict Neonatal Macrosomia Differ from Those that Predict Postpartum Prediabetes or Diabetes: Implications for the Diagnostic Criteria for Gestational Diabetes

Leadership Sinai Centre for Diabetes (R.R., Y.Q., A.J.G.H., B.Z.) and Division of Obstetrics and Gynecology (M.S.), Mount Sinai Hospital, Toronto, Canada M5T 3L9; Division of Endocrinology (R.R., P.W.C., A.J.G.H., B.Z.) and Department of Nutritional Sciences (A.J.G.H.), University of Toronto, Toronto, Canada M5S 3E2; and Keenan Research Centre in the Li Ka Shing Knowledge Institute of St. Michael’s Hospital (P.W.C.), Toronto, Canada M5B 1W8

Address all correspondence and requests for reprints to: Dr. Ravi Retnakaran, Leadership Sinai Centre for Diabetes, 60 Murray Street, Suite L5-039, Mailbox 21, Toronto, Ontario, Canada M5T3L9. E-mail: rretnakaran{at}mtsinai.on.ca.

Background/Objective: The diagnosis of gestational diabetes mellitus on oral glucose tolerance test (OGTT) is used to identify risk of both neonatal large-for-gestational-age (LGA) and maternal postpartum prediabetes/diabetes. An assumption inherent in this practice, however, is that the glucose values that define gestational diabetes mellitus on the OGTT relate to both of these outcomes in the same way. Thus, to test this assumption, we sought to evaluate the predictive capacity of each glucose value on antepartum OGTT in relation to LGA and postpartum prediabetes/diabetes.

Design/Setting/Participants: A total of 412 women representing the full spectrum of antepartum glucose tolerance underwent 3-h OGTT in pregnancy, assessment of obstetrical outcome at delivery, and 2-h OGTT at 3 months postpartum.

Results: Of the four glucose values (fasting, 1h, 2 h, 3 h) on antepartum OGTT, only the fasting measure was a significant predictor of LGA [odds ratio (OR) 2.00 per mmol/liter, 95% confidence interval (CI) 1.20–3.34] (P = 0.0076). In contrast, all three postload glucose values were significant predictors of postpartum prediabetes/diabetes (1 h glucose: OR 1.37, 95% CI 1.17–1.61, P < 0.0001; 2 h glucose: OR 1.55, 95% CI 1.32–1.83, P < 0.0001; 3 h glucose: OR 1.30, 95% CI 1.10–1.53, P = 0.002), whereas fasting glucose was not. Furthermore, whereas fasting glucose had the highest area under the receiver operating characteristic curve for predicting LGA (0.62), the 1- and 2-h glucose measures had the highest area under the receiver operating characteristic curve values for postpartum prediabetes/diabetes (0.68 and 0.72, respectively).

Conclusions: On antepartum OGTT, the fasting glucose value best predicts LGA risk, whereas postload glucose values predict postpartum prediabetes/diabetes. These relationships may have implications for the glycemic thresholds that define obstetrical and metabolic risk.