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Use of tocolytic therapy to stop uterine contractions can prolong pregnancy and prevent preterm birth

Treatment of preterm labor with bed rest, hydration, medication, and combinations of these interventions may be used to prevent preterm birth, the leading cause of infant death and serious problems. Tocolytic drugs are typically used to stop uterine contractions during an episode of preterm labor (first-line therapy) or to maintain uterine quiescence after an acute episode (maintenance therapy).

Management of uterine contractions with first-line tocolytic therapy can prolong gestation. However, maintenance tocolytic therapy has little or no value, according to a study funded by the Agency for Healthcare Research and Quality (contract 290-97-0011). Kathleen N. Lohr, Ph.D., and colleagues at the Research Triangle Institute/University of North Carolina at Chapel Hill Evidence-based Practice Center evaluated 256 studies of women with preterm labor between 1966 and 1999.

The researchers performed a meta-analysis on 16 studies of first-line tocolytic therapy and 8 studies of maintenance therapy to evaluate evidence on the benefits and harms of five classes of tocolytic therapy for treating uterine contractions related to preterm labor: beta-mimetics, calcium channel blockers, magnesium, nonsteroidal antiinflammatory agents, and ethanol. The studies of first-line tocolytics (with fair strength of evidence) revealed a mixed outcome pattern with small improvement in pregnancy prolongation and birth at term relative to placebo. Data were insufficient to show a direct beneficial effect on neonatal problems or deaths.

Maintenance tocolytics (poor strength of evidence) showed no improvements in birth or infant outcomes relative to placebo.

All tocolytics were rated as low-risk for short-term neonatal harms. However, beta-mimetics appear to be no better than other drugs and pose significant potential harms to mothers (for example, serious cardiac problems, metabolic abnormalities, and jitteriness). Ethanol was less beneficial than other drugs and remains an inappropriate therapy.

More details are in "Tocolytic treatment for the management of preterm labor: A review of the evidence," by Nancy D. Berkman, Ph.D., John M. Thorp, Jr., M.D., Dr. Lohr, and others, in the American Journal of Obstetrics & Gynecology 188(6), pp. 1648-1659, 2003.

Editor's Note: Copies of the Evidence Report/Technology Assessment No. 18, Management of Preterm Labor summary (AHRQ Publication No. 01-E020) are available from the AHRQ Publications Clearinghouse, and the full report (AHRQ Publication No. 01-E021) is available from the AHRQ Publications Clearinghouse.

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