Sinusoidal fetal heart rate patterns were observed in 42.5% of a group of 40 women who had received alphaprodine (Nisentil) for relief of labor pain. Analysis showed that the pattern appeared approximately 19 minutes following alphaprodine administration and persisted for approximately 60 minutes. In a control group of 18 patients who did not receive narcotic analgesia, an intermittent sinusoidal pattern was observed in one patient. All babies with sinusoidal heart rate during labor had 1-minute Apgar scores of 7 or greater except two in the study group. Both these neonates had low Apgar scores directly associated with complications at delivery. All 5-minute Apgar scores were 7 or greater, and there were no perinatal deaths.