Sinusoidal fetal heart rate associated with maternal administration of meperidine and promethazine in labor

Sinusoidal heart rate pattern has been associated with high neonatal morbidity. We studied the incidence and the prognostic value of sinusoidal heart rate after the administration i.v. to the mother of 50 mg of meperidine and 25 mg of promethazine to relieve pain in labor. For this purpose we analysed 350 FHR records from patients treated in labor with these pharmacological substances; we found 11 sinusoidal patterns (3.2%): The mean onset time after the injection of the drug was 13.2 ± 18.1 minutes; the mean duration was 26.5 ± 20.6 minutes. There was only one newborn with slight RDS after delivery. There were not perinatal death or serious morbidity. It is well known that meperidine and promethazine may induce modifications of FMR without pathological fetal conditions: SHR can also appear probably because of an effect on autonomic cardioregulatory centers, caused by the drugs and not by hypoxia. In these cases the interruption of the labor is not indicated.