Active phase labor arrest: revisiting the 2-hour minimum.

OBJECTIVE: To generate contemporary uterine activity and labor progress data for oxytocin-augmented labor, and assess whether 2 hours of active phase labor arrest with at least 200 Montevideo units justifies cesarean delivery. METHODS: Five hundred and one consecutive spontaneously laboring term women with abnormally progressive labor were managed by a standardized protocol: oxytocin and intrauterine pressure catheter with an intent to sustain at least 200 Montevideo units for 4 hours or more before cesarean for labor arrest. Uterine activity was measured, and maternal and neonatal outcomes were evaluated. With a sample of this size, the upper 95% confidence interval limit for an event with an observed rate of 1% is below 3%. RESULTS: During oxytocin augmentation, nulliparas who were delivered vaginally dilated at a median rate of 1.4 cm/hour versus 1.8 cm/hour for parous women. In both groups, the 5th percentile of cervical dilation rate was 0.5 cm/hour. Thirty-eight women experienced labor arrest for over 2 hours despite at least 200 sustained Montevideo units; 23 (61%) achieved a vaginal delivery. Rates of chorioamnionitis and endometritis for the 38 women were 26%. None of their infants sustained a serious complication, including brachial plexus injury, even though three of the 23 vaginal deliveries (13%) were complicated by shoulder dystocia. CONCLUSION: These data demonstrate that oxytocin-augmented labor proceeds at substantially slower rates than spontaneous labor, and support our previous contention that the criteria of labor arrest for 2 hours, despite at least 200 sustained Montevideo units, are insufficiently rigorous for the performance of cesarean.

Cardiovascular effects of intravaginal misoprostol in the mid trimester of pregnancy.

OBJECTIVE: Our aim was to evaluate the cardiovascular effects of high-dose intravaginal misoprostol administration by means of transthoracic electrical bioimpedance monitoring. STUDY DESIGN: Healthy women undergoing mid trimester pregnancy interruption with intravaginal misoprostol were eligible for this prospective observational study. Baseline blood pressure was obtained for 1 hour and transthoracic electrical bioimpedance monitoring was performed before misoprostol administration, 600 microg vaginally. Posttreatment assessments were made every 15 minutes for a total of 4 hours, with patients in a left lateral recumbent position. Heart rate, mean arterial pressure, cardiac index, stroke index, systemic vascular resistance index, and end-diastolic volume index were determined. Measurements were averaged for 30-minute intervals and reported as mean +/- SD. Statistical analyses included the paired t test and repeated-measures analysis of variance. RESULTS: Nine women consented to have transthoracic electrical bioimpedance monitoring, and no statistically significant changes in any of the measured cardiac parameters for the 4-hour monitoring interval were noted. Direct comparisons between the pretreatment and 2-hour posttreatment intervals (reported time peak of blood misoprostol levels) also revealed no significant differences in the cardiovascular index values. CONCLUSION: High-dose intravaginal misoprostol in the mid trimester does not alter maternal cardiac function as measured by transthoracic electrical bioimpedance.