Acute tocolysis for intrapartum nonreassuring fetal status: how often does it prevent cesarean delivery? A systematic review and meta-analysis of randomized controlled trials

OBJECTIVE: This study aimed to evaluate the effectiveness of intrapartum acute tocolysis for nonreassuring fetal heart rate tracing in decreasing the incidence of cesarean delivery. Secondary outcomes included modes of delivery other than cesarean delivery, successful acute tocolysis, time-to-delivery interval, and short-term perinatal outcomes. DATA SOURCES: Searches were performed in MEDLINE/PubMed, Embase, Scopus, the Cochrane Central Register of Controlled Trials and Reviews, ClinicalTrials.gov, and the International Clinical Trials Registry Platform from the inception of each database until February 2022. STUDY ELIGIBILITY CRITERIA: Selection criteria included randomized controlled trials of laboring patients with singleton gestations randomized to receive intrapartum acute tocolysis for nonreassuring fetal heart rate tracing, as defined by the original trial. METHODS: All analyses were done using an intention-to-treat approach, evaluating women according to the treatment group to which they were randomly allocated in the original trials. A frequentist network-meta-analysis was performed. RESULTS: Four randomized clinical trials were eligible, including 605 patients with nonreassuring fetal heart rate tracing and singleton gestations at gestational ages >32 weeks. The cesarean delivery rate was similar among patients managed with different types of acute tocolysis. Acute tocolysis, compared with emergency delivery, was associated with improved neonatal acid-base status (notably decreasing the prevalence of base deficit >12 mmol/L [beta-2 agonists odds ratio, 0.61; 95% confidence interval, 0.37–0.99] and the rate of neonatal intensive care unit admission [beta-2 agonists odds ratio, 0.42; 95% confidence interval, 0.22–0.78]) and with an increase in the time-to-delivery interval (beta-2 agonists mean difference, 17.62 minutes; 95% confidence interval, 15.66–19.58); there was no reduction of cesarean delivery rate, showing an increased rate with atosiban and beta-2 agonists. CONCLUSION: The cesarean delivery rate was not reduced by acute tocolysis when used for nonreassuring fetal heart rate tracing during labor. Acute tocolysis is associated with improved short-term fetal outcomes and safely increases the time-to-delivery interval.