AbstractsElectronic fetal heart rate (FHR) monitoring was developed to improve detection of intrapartum fetal distress, but its efficacy has never been fully demonstrated. In 1979, a national task force recommended randomized clinical trials of patients with high-risk pregnancies (particularly preterm labor) to determine the effect of fetal heart rate monitoring on perinatal mortality and morbidity and maternal morbidity. In 1981, the present authors began such a trial, combining electronic fetal heart rate monitoring with fetal scalp sampling, in patients with preterm labor. They compared the results with those obtained by auscultation alone. The purpose of the trial was to determine whether electronic fetal heart rate monitoring was associated with a clinically important improvement in perinatal mortality and neurodevelopment at 18 months of (corrected) age.The study was conducted at three different referral centers, and a total of 376 patients were enrolled (188 for electronic monitoring and 188 for auscultation). Of these patients, 246 delivered infants weighing 1750 gm or less. The investigation was confined to this group of infants.There were no significant differences between the electronic monitoring and the auscultation groups in the number of patients exposed to tocolytic agents (65 vs. 77, respectively), antenatal glucocorticoids (48 in each group), oxytocin (41 vs. 50), or regional anesthesia (56 vs. 53). Monitoring technique was not associated with premature rupture of membranes, which occurred in 68 of 122 patients (56 per cent) in the electronic monitoring group and in 58 of 124 patients (47 per cent) in the auscultation group. Monitoring technique did not influence medical intervention during labor.The primary cesarean section rate was 16 per cent with electronic fetal heart rate monitoring and 15 per cent with periodic auscultation. These levels are compatible with the institutional cesarean section rates for cephalic pregnancies in the birth weight range. Fetal distress (ominous fetal heart rate) was the most common indication for cesarean section. The operation was performed for that reason in 8.2 per cent of the patients with electronic monitoring and in 5.6 per cent of those with periodic auscultation. Fetal distress was observed more frequently in the electronic monitoring group (27 per cent) than in the auscultation group (15 per cent), but the difference was not significant (P = 0.08). The second most common indication for cesarean section was noncephalic presentation.The condition of the infant, as judged by Apgar score and the acid-base characteristics of blood specimens obtained from the umbilical cord at birth, was not significantly different in the two monitoring techniques. Fetal acidosis and low 5-minute Apgar scores were uncommon (less than 10 per cent), regardless of monitoring technique. The frequency of neonatal seizures, severe respiratory distress syndrome, and intracranial hemorrhage were not significantly different in the two groups.Thirty-five perinatal or infant deaths occurred: 17 after electronic fetal heart rate monitoring (13.9 per cent) and 18 after auscultation (14.5 per cent). All deaths occurred in infants with birth weights less than 1500 gm. Monitoring technique was not associated with a significant difference in mortality in any birth weight category. Of the 35 deaths, 28 were associated with cardiopulmonary failure and hyaline membrane disease. Of the seven remaining deaths, three were due to congenital anomalies that were unrecognized antenatally, two in the electronic monitoring group (renal agenesis and trisomy 18) and one in the auscultation group (diaphragmatic hernia and omphalocele). There were two infant deaths in the auscultation group due to pneumonia, and there was one stillbirth in each group.There were 14 perinatal deaths among 119 electronic fetal heart rate monitoring patients (11.8 per cent) and 14 among 120 auscultated patients (11.7 per cent).Thirty per cent of the patients with electronic fetal heart rate monitoring had significant maternal morbidity, as compared with 36 per cent of those with periodic auscultation (a nonsignificant difference). Nonsignificant differences also were found for specific causes of maternal morbidity, including blood transfusion, endometritis, laceration, wound infection, and urinary tract infection. There was no fetal morbidity directly attributable to either monitoring technique.