Reactivity of non-stress tests and its relationship to outcome in infants born prior to the 33rd week of gestation.

Abstract

In order to evaluate the significance of the non-stress test (NST) in the immature fetus, 60 patients who gave birth between the 26th and 33rd week of gestation were studied. They were grouped according to reactivity of the last non-stress test performed 24 hours prior to delivery. Twenty-eight (47%) of the patients were reactive, 10 (17%) non-reactive, and 22 (37%) non-reactive with decelerations on the last NST. The one-year mortality rates were significantly higher in those non-reactive with decelerations (41%) and in those non-reactive (30%), than in the reactive group (7%) (p less than 0.001, p less than 0.05). The results suggest that reactive non-stress tests and those that are non-reactive with decelerations predicted the fetal outcome similarly to the same findings in term pregnancies. Non-reactive non-stress tests without decelerations were associated with poor outcome in fetuses with a gestational age of more than 29 weeks. Conversely, in more immature fetuses, nonreactive patterns occurred in patients with favorable outcome. The clinical implications of these findings are discussed.