Effectiveness of Tocolytic Agents on Prevention of Preterm Delivery, Neonatal Morbidity, and Mortality: Is There a Consensus? A Review of the Literature

Preterm delivery presents the main cause of neonatal morbidity and mortality worldwide. The rate of preterm delivery is 12% to 13% in the United States, of which 29% concerns preterm deliveries before 34 weeks of gestation. Basic parameter of prevention strategy is implementation of tocolytic therapy in cases of threatened preterm labor. Several therapeutic approaches have been proposed, among which betamimetic agonists, calcium channel blockers, magnesium sulfate, oxytocin receptor blockers, nitrates, and prostaglandin inhibitors, whereas new alternatives such as usage of thiocolchicoside have also been reported. This article is one among few that aims to review the comparative effectiveness of various tocolytic agents regarding prevention of preterm delivery, impact on perinatal morbidity and mortality, neonatal health status, and maternal complications. Main conclusions of recent randomized control trials and meta-analyses are summarized to assess about which agents consensus already exists on their effectiveness, which agents should be further studied to achieve conclusions, as well as those that are rather unlikely to have significant tocolytic impact or any other benefit on neonatal outcome. Target Audience Obstetricians and gynecologists, family physicians Learning Objectives After completing this activity, the learner should be better able to be informed that oral betamimetics may have a positive impact only to postpone preterm delivery for at least 48 hours. However, no significant advantage is indicated on any of the examined parameters of neonatal morbidity and mortality; understand that no significant benefit of calcium channel blockers on neonatal morbidity and mortality parameters may be supported, despite the potential benefit on prolongation interval; be informed that oxytocin receptor antagonists do not present significant tocolytic effect and are not associated with significant improvement of neonatal morbidity and mortality parameters; highlight that there are strong indications that progesterone administration is effective on preventing preterm delivery as well as improving neonatal morbidity and mortality; and be informed that antibiotics may not be suggested as a tocolytic therapy and their usage should rather be restricted in cases with preterm premature rupture of membranes to prevent chorioamnionitis.