Clinical sequelae of the extended nonstress test

Abstract

Two hundred eighty-one high-risk gravida women undergoing a collective total of 661 nonstress tests entered a protocol to determine whether extending initially nonreactive tests improved the positive predictive value of this test modality. Reactivity required the occurrence of at least three fetal heart rate accelerations (15 bpm, 15 seconds' duration), associated with fetal movement during a 30-minute episode. Tests failing these criteria were extended by sequential 30-minute increments until a reactive 30-minute window appeared or 90 minutes had elapsed. After 90 minutes, a nonreactive test was followed by a contraction stress test. Reactive tracings occurred in 266 patients (95%) and in all cases were evident by the end of 70 minutes. Corrected perinatal mortality and morbidity in this group were 0% and 5.6%, respectively. Nonreactive fetuses not only produced abnormal (positive or persistently equivocal) contraction stress tests in nearly all cases (93.3%) but had mortality and morbidity rates of 6.7% and 93.3%, respectively. Furthermore, in five of 15 instances, the contraction stress test was associated with profound fetal heart rate decelerations necessitating emergency delivery. We conclude that prolonged nonreactivity, in the absence of significant immaturity, congenital abnormalities, or pharmacologic agents, identifies significant fetal jeopardy. Expeditious termination of pregnancy should be considered and, under these circumstances, a subsequent contraction stress test may be relatively contraindicated.