Effect of the 100-g oral glucose tolerance test on fetal acid-base balance

Objective: Previous studies have shown that maternal hyperglycemia may lead to fetal hypoxia and acidosis. The aim of the present study was to examine the impact of an oral 100-g glucose tolerance test on the fetal acid-base balance at mid-gestation. Methods: The study was conducted in healthy women who were scheduled for termination of pregnancy. The study group (n = 18) received an oral solution containing 100-g glucose and the control group (n = 18) received only water 1 h prior to termination of pregnancy. Termination of pregnancy was performed by fetal intracardiac injection of potassium chloride (KCl) and intraamniotic instillation of PGF2α. Acid-base variables were evaluated in the fetal blood and the amniotic fluid. Results: The glucose levels differed significantly between the study group and the control group with regard to maternal blood (127 ± 28 versus 69 ± 11 mg/dL, p < 0.001), fetal blood (128 ± 24 versus 71 ± 17 mg/dL, p < 0.001) and amniotic fluid (39 ± 13 versus 28 ± 5 mg/dL, p < 0.006). A linear relationship was found between maternal, fetal and amniotic fluid levels of glucose after maternal glucose ingestion. No significant changes were observed in the acid-base balance variables (pH, base excess, bicarbonate, lactate) in the fetal blood and the amniotic fluid of the study and control groups. Conclusion: The 100-g oral glucose tolerance test has no adverse effect on the fetal acid-base balance when glucose levels reach a peak 1 h after the test in normal pregnancies.