Sinusoidal fetal heart rate pattern: its definition and clinical significance.

A review was made of the available literature on the sinusoidal heart rate (SHR) pattern. A specific definition of SHR was made in order to elucidate its clinical significance. According to this definition 41 tracings from 23 publications were classified as being either true SHR, equivocal, or a heart rate pattern other than SHR. On the basis of this definition, 27 tracings were classified as true SHR patterns and all were associated with significant fetal or neonatal morbidity or mortality, except in two cases after administration of alphaprodine. Three tracings were judged to be equivocal. In two other cases the fetal heart rate tracings were classified as nonsinusoidal premortem patterns associated with poor perinatal outcome. As for the other nine tracings that did not meet the proposed definition, the perinatal outcome was normal. Therefore, because of a stricter definition of jeopardy, except when the SHR pattern appears after induction of analgesia with alphaprodine.