Nonstress testing and perinatal outcome

Abstract

The clinical value of nonstress testing (NST) in assessing fetal well-being is controversial. This study reviews the monitored tracings and subsequent perinatal outcome of 561 high-risk clinic patients who had undergone NST within one week prior to delivery. Two or more adequate accelerations of the fetal heart rate baseline with sufficient fetal activity over a 20-minute period were associated with a low risk of fetal jeopardy and were classified as a reactive test result. The corrected perinatal mortality of patients with reactive NSTs (1/509) was comparable to that of patients with no apparent antepartum complications (6/1,408) and was significantly lower (p less than 0.05) than those of high-risk patients with either nonreactive NSTs (2/22) or no testing (20/1,000). The incidence of subsequent perinatal jeopardy was significantly lower (p less than 0.001) among those high-risk pregnancies with recent reactive NST results (4%) than in those with recent nonreactive NST results (36%) and those without recent testing (13%). Perinatal morbidity among those pregnancies with recent reactive NSTs usually arose in the intrapartum period, and no reason to explain this jeopardy predominated. A reactive NST can be safely repeated in seven days, regardless of the adequately treated maternal risk factor. The only stillbirth following a reactive NST (1/509) probably arose from a cord accident.