Loss of beat-to-beat variability and a negative oxytocin challenge test: an ominous prognostic sign.

The reputation of the predictive accuracy of a negative oxytocin challenge test (OCT) has been somewhat tarnished by recent sporadic reports of intrauterine fetal death relatively soon after a negative OCT. We have analyzed probable causes and the possibilities of reducing to a minimum "false-negative" results of the OCT. In particular, several of these reports did not take into account the loss of baseline fetal heart rate (FHR) variability recorded during the OCT and, in the absence of late decelerations, the OCT was interpreted as negative. We suggest that recordings showing a loss of baseline beat-to-beat FHR variability and a negative OCT illustrate a complete inability of the fetus to react to any stimulus and that, in these cases, a negative OCT should in no way be reassuring, but rather a warning sign of severe fetal compromise. Two cases are presented to illustrate this phenomenon.