Diurnal nonstress test variations in the human fetus at risk

Objective: To compare the results of the nonstress test (NST) performed at 9:00 PM and 9:00 AM on women with high-risk pregnancies. Method: The NST was performed 2 h after a meal, at 9:00 AM and 9:00 PM, in a quiet room exposed to daylight, on 80 women with high-risk singleton pregnancies. Each session lasted 20 min. If the NST was nonreactive, the entire biophysical profile was immediately performed. The women's blood pressure was measured before, 10 min within, and at the end of the NST. Women who smoked or had uterine contractions were excluded from the study. Results: Diurnal nonstress test variations were manifested by a higher incidence of reactive NSTs and an increased number of fetal heart accelerations after 9:00 PM (82.5%) than at 9:00 AM (68.8%) (p < 0.027 P < 0.001). Conclusions: Evening appointments for fetal assessments, except in emergency conditions, may eliminate the need for additional tests such as the entire biophysical profile because of the decreased incidence of nonreactive NSTs. Evening NSTs would save time and decrease maternal anxiety.