Can glucose tolerance test predict fetal hyperinsulinism?

Abstract

To establish cut off levels for oral glucose tolerance test in pregnancy using fetal hyperinsulinism as a clinical endpoint. Capillary blood glucose levels at 0, 1, and 2 hours after the ingestion of either 1 g/kg or 75 g glucose, at 28 (SD 5) weeks of gestation were analysed in 220 women with elevated amniotic fluid insulin levels [> or =42 pmol/L (> or =7 microU/mL)] after a mean (SD) of 31 weeks (3) and in 220 nondiabetic controls. In women with elevated amniotic fluid insulin levels the mean (SD) capillary blood glucose values at 0, 1, and 2 hours were 5.2 mmol/L (1.0) [94 mg/dL (18)], 10.5 mmol/L (1.4) [189 mg/dL (25)] and 8.2 mmol/L (2.0) [147 mg/dL (36)], respectively. The one-hour value had the highest sensitivity to predict elevated amniotic fluid insulin levels. The 5th centile of the one-hour blood glucose levels representing a detection rate of 95% was 8.9 mmol/L (160 mg/dL). Glucose cut off levels in most established oral glucose tolerance test criteria are too high, to accurately predict amniotic fluid hyperinsulinism. A one-hour test may be sufficient for detecting amniotic fluid hyperinsulinism. Since different loads (1 g/kg, 75 g or 100 g) and blood fractions (venous plasma or capillary blood) have minimal impact on oral glucose tolerance test results, a single one-hour cut off of 8.9 mmol/L (160 mg/dL), independent of the sampling method, may be appropriate for the diagnosis of gestational diabetes mellitus severe enough to cause amniotic fluid hyperinsulinism.