Diurnal non-stress test variations in healthy term fetuses. A call for evening appointments for fetal testing.

Abstract

The null hypothesis is that the time of day during which non-stress testing is performed does not influence the reactivity of the test. Fetal heart rate (FHR) monitoring was performed in 65 healthy term fetuses at 09:00, 14:00 and 21:00 h, in a quiet room exposed to daylight 2 h after maternal meals. Each session lasted 20 min. Smoking mothers were excluded. Statistical analysis was performed using a double-tailed t-test. Diurnal non-stress test (NST) variations exist and are manifested by a higher incidence of a reactive NST at 21:00 h compared to a 09:00 h assessment, and an increased number and longer duration of accelerations during a 20-min observation period at 21:00 h compared to a 09:00 h assessment. Evening appointments for fetal assessments may eliminate the need for additional tests due to the decreased incidence of nonreactive NSTs. These in turn will decrease both maternal anxiety and the expense of further testing.