The effect of maternal glucose administration on the specificity of the nonstress test

To determine whether maternal glucose administration can decrease the incidence of false positive nonstress tests, 296 nonstress tests were performed on 235 high-risk obstetric patients in a prospective controlled study. Patients were alternately given a 50 gm oral glucose drink or an equal volume of water 30 minutes prior to the commencement of each test. Among “fed” patients (last meal within 2 hour of the nonstress test) whether receiving glucose or water, and “fasted” patients who received glucose, there was no significant difference in the percentage of reactive tests at either 20 minutes (65.2%) or 40 minutes (87.3%) of testing. However, patients fasting and receiving water had a significantly decreased percentage of reactive tests, both at 20 minutes (48.3%, P < 0.01) and at 40 minutes (76.7%, P < 0.05). Glucose administered to fasted patients resulted in an increase in the incidence of reactive tests, although this was not statistically significant. Glucose administration had no effect on the nonstress test results when administered to fed patients.