Antepartum fetal heart rate testing: the nonstress test

Antepartum assessment of fetal well being relies heavily on the observation of RHR. Fetal stress testing was introduced in the early 1970's in an attempt to define the fetus at risk. The stress factor most widely used has been uterine contractions, which isolate the fetus from its oxygen supply, and in the compromised fetus would be anticipated to provoke late decelerations in the FHR. Although the contraction stress test or "oxytocin challenge test" is useful in evaluating fetal condition, it is time consuming, not easily quantitatable or repeatable, and many times difficult to interpret. An attractive alternate approach of antepartum FHR testing (AFHRT) is the "nonstress" test. The positive experience of European investigators has led to interest in this method of fetal assessment in North America. Investigation from the literature contrasting the "stress" versus "nonstress" methods is discussed and observations derived from 2 year experience at LAC/USC Medical Center are presented. A protocol for AFHRT currently being evaluated clinically is presented.