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Inhibition of acute preterm labor

Hyagriv N Simhan, MD, MS
Steve Caritis, MD
Section Editor
Charles J Lockwood, MD, MHCM
Deputy Editor
Vanessa A Barss, MD, FACOG


This topic will discuss use of tocolytic drugs for inhibition of acute preterm labor. Other issues related to preterm labor, including pathogenesis, risk factors, clinical manifestations and diagnosis, diagnostic evaluation, prevention, and neonatal outcome, are reviewed separately.

(See "Preterm birth: Risk factors and interventions for risk reduction".)

(See "Diagnosis of preterm labor".)


Administration of tocolytic drugs can reduce the strength and frequency of uterine contractions. In women with acute preterm labor, a 2009 meta-analysis of randomized trials found that these drugs were more effective than placebo/control for delaying delivery for 48 hours (75 to 93 percent versus 53 percent for placebo/control) and for seven days (61 to 78 percent versus 39 percent for placebo/control), but not for delaying delivery to 37 weeks [1]. Notably in this meta-analysis [1] and others [2], a substantial proportion of women diagnosed with preterm labor (about 50 percent) did not deliver in the short-term, or even preterm, when tocolytic therapy was not administered. Furthermore, administration of tocolytic drugs did not result in statistically significant reductions in important clinical outcomes, such as neonatal respiratory distress and survival [1].


General principles — Women in the early phases of acute preterm labor, when cervical dilation is not advanced, are optimum candidates for tocolytic therapy [3]. Tocolysis is indicated when the overall benefits of delaying delivery outweigh the risks. In a practice bulletin, the American College of Obstetricians and Gynecologists opined: "Interventions to reduce the likelihood of delivery should be reserved for women with preterm labor at a gestational age at which a delay in delivery will provide benefit to the newborn. Because tocolytic therapy is generally effective for up to 48 hours, only women with fetuses that would benefit from a 48 hour delay in delivery should receive tocolytic treatment" [4].

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Literature review current through: Nov 2017. | This topic last updated: Nov 03, 2017.
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