Effect of vacuum extraction on umbilical cord blood acid-base measurements.

The objective of this study was to determine whether vacuum extraction is associated with umbilical cord blood acid-base changes when used electively or in the presence of suspected fetal distress. Data from 1,428 patients from a previously published randomized trial of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation were analyzed to identify differences in umbilical cord blood acid-base measurements associated with the elective use of vacuum extraction (patients with duration of second stage of labor 60 min or less) and also in the presence of suspected fetal distress during the second stage of labor. When used electively, vacuum extraction was associated with lower pH (in both umbilical cord artery and vein), lower venous base excess, and higher venous carbon dioxide tension (PCO2), as compared to normal spontaneous vaginal delivery. After correcting for duration of second stage of labor, elective vacuum delivery was significantly associated only with a decrease in cord venous pH and increase in venous PCO2. However, these cord blood acid-base changes were not accompanied by any differences in perinatal morbidity and mortality or in the number of neonates born with acidemia (cord arterial pH < 7.15 or < 7.10). In cases of suspected fetal distress, the use of vacuum extraction was not associated with any detectable cord blood acid-base changes as compared to normal spontaneous vaginal delivery. These data support the continued use of vacuum extraction, especially in cases of suspected fetal distress during the second stage of labor.

Comparison of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation in detecting fetal acidemia at birth.

OBJECTIVE: Our purpose was to compare continuous intrapartum electronic fetal heart rate monitoring with intermittent auscultation for detecting fetal acidemia at birth. STUDY DESIGN: Data from a previously published randomized trial of electronic fetal heart rate monitoring versus intermittent auscultation were analyzed to identify any differences between the two methods in detecting fetal acidemia at birth. Fetal acidemia at birth was defined as the presence of cord blood arterial pH < 7.15. RESULTS: A total of 1419 patients with umbilical cord blood acid-base measurements were identified, 739 in the electronic FHR monitoring group and 680 in the auscultation group. Electronic FHR monitoring had significantly better sensitivity (97% vs 34%, p < 0.001), lower specificity (84% vs 91%, p < 0.001), higher positive predictive value (37% vs 22%, p < 0.05), and higher negative predictive value (99.5% vs 95%, p < 0.001) in detecting fetal acidemia at birth. In addition, electronic FHR monitoring was significantly better in detecting all types of acidemia: metabolic (95.5% vs 26.5%, p < 0.001), mixed (95% vs 37.5%, p < 0.001), and respiratory (100% vs 41.5%, p < 0.001). CONCLUSION: These data suggest that electronic FHR monitoring is superior to intermittent auscultation in detecting fetal acidemia at birth.

A randomized trial of intrapartum electronic fetal heart rate monitoring versus intermittent auscultation.

OBJECTIVE: To determine whether continuous intrapartum electronic fetal heart rate monitoring (EFM) is associated with decreased perinatal mortality and morbidity compared with intermittent auscultation. METHODS: The study was conducted simultaneously at two university hospitals in Athens, Greece (Alexandra and Marika Iliadi Hospitals) from October 1, 1990 to June 30, 1991. All patients with singleton living fetuses and gestational ages of 26 weeks or greater were eligible for inclusion. The participants were assigned to continuous EFM or intermittent auscultation based on the flip of a coin. Both groups were followed during labor according to the most recent ACOG guidelines. However, fetal scalp blood pH and crossover from one group to the other were not used. RESULTS: A total of 1428 patients were included, 746 in the EFM group and 682 in the auscultation group. There were no differences between the groups in terms of maternal age, gravidity, parity, gestational age, and number of antepartum high-risk factors. More patients monitored electronically received oxytocin for either augmentation (52.4 versus 38.1%; P = .0001) or induction (15.6 versus 7%; P = .0001). The length of labor was longer in the EFM group (first stage 6.1 +/- 4.3 versus 5.5 +/- 3.7 hours; P = .006; second stage 29.4 +/- 18.6 versus 26.9 +/- 16.9 minutes; P = .01). There was a higher incidence of nonreassuring fetal heart rate patterns in the EFM group (23.4 versus 10.7%; P = .0001) and a higher rate of surgical intervention (11.2 versus 4.8%; P = .0001). This difference pertained to both vacuum extraction (5.8 versus 2.4%; P = .002) and cesarean delivery for suspected fetal distress (5.3 versus 2.3%; P = .005). There were no differences in 1- and 5-minute Apgar scores, fetal acidosis at birth, need for neonatal resuscitation, neonatal intensive care unit admission, use of assisted ventilation, neonatal hospital stay, or any other neonatal complications. Two neonatal deaths occurred in the EFM group and nine perinatal deaths in the auscultation group (two intrapartum and seven neonatal deaths). The perinatal mortality rates were 2.6 per 1000 and 13 per 1000 total births, respectively (P = .04). The two deaths in the EFM group and three of the neonatal deaths in the auscultation group may not have been prevented by intrapartum monitoring; however, four neonatal deaths from the auscultation group occurred in depressed (5-minute Apgar scores less than 7), acidotic (cord artery pH at or below 7.13) infants. The perinatal death rate related to fetal hypoxia was significantly less in the EFM group (zero of 746 versus six of 682; P = .03). CONCLUSION: In this controlled trial, intrapartum EFM, as the primary and only method of intrapartum fetal surveillance, was associated with decreased perinatal mortality due to fetal hypoxia but also with higher rates of surgical intervention for suspected fetal distress.