Fetal biophysical testing. The effects of prolonged maternal fasting and the oral glucose tolerance test.

Fetal biophysical testing incorporates observations of the fetal heart rate (FHR), fetal breathing movements (FBMs) and fetal trunkal movements (FTMs). These parameters were examined during maternal fasting and glucose loading. Thirty normal term gravidas were studied during a 210-minute session, of which the first 30 minutes served as a fasting control period, following which 20 (group G) received 100 g oral glucose, while 10 (group F) continued fasting. Serum glucose levels in both groups were determined every 30 minutes. FHR, FBMs and FTMs were recorded concurrently using abdominal electrocardiography and real-time ultrasonography and entered on line into a microcomputer. Offline data analysis provided mean 30-minute baseline FHRs, acceleration counts, FBM incidences, FBM rates and FTM incidences. Both groups were similar for gestational age, birth weight and perinatal outcomes. Mean 30-minute FHR baseline was unchanged and similar in both groups. Mean 30-minute FHR acceleration counts and FTM incidences were significantly higher in group F, while FBM incidences and rates were significantly higher in group G. While biophysical testing can be conducted under either set of maternal conditions, different normal standards must be employed, test length must be sufficient to account for normal biologic variations, and biophysical parameters must be monitored concurrently.