Rapid infusion of large amount of glucose is associated with fetal hyperglycemia, hyperinsulinemia, and neonatal hypoglycemia. However, the effect of small dose of glucose is unclear. We conducted a pilot study of small dose of glucose. We investigated the effect of a glucose-containing fluid on the blood sugar of the umbilical artery. We found that in the case of no-glucose-containing fluid, there were some cases in which umbilical arterial concentration of glucose was less than 50 mg/dl, which might cause neonatal hypoglycemia. In addition, in the case of 1%-glucose-containing fluid, mean umbilical arterial concentration of glucose was 97 mg/dl.