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Am Fam Physician. 2007;75(5):648-649

Author disclosure. Nothing to disclose.

Clinical Scenario

A pregnant patient presents to the hospital at 31 weeks' gestation with preterm contractions. After the patient receives hydration and terbutaline (Brethine), the contractions stop.

Clinical Question

Should an oral betamimetic be used as maintenance therapy to prevent preterm delivery after treatment for threatened preterm labor?

Evidence-Based Answer

There is no evidence to support the use of oral betamimetics for maintenance therapy after treatment for threatened preterm labor, and there is a risk of adverse effects with these drugs.1

Practice Pointers

Despite the lack of evidence of their effectiveness and the potential for adverse effects, many physicians continue to use betamimetics. This Cochrane review included 11 randomized controlled trials (RCTs) with a total of 1,238 women. Eight of the RCTs compared an oral betamimetic with placebo or no treatment, one compared an oral betamimetic with the nonsteroidal anti-inflammatory drug indomethacin (Indocin), one compared two betamimetics, and three compared an oral betamimetic with magnesium (some trials had more than two arms). The precision of the results is somewhat low because serious outcomes were uncommon; however, the consistency of the results lends weight to their validity.

The American College of Obstetricians and Gynecologists (ACOG) guideline on the management of preterm labor states that there is good and consistent evidence that “neither maintenance treatment with tocolytics [such as betamimetics] nor repeated acute tocolysis improves perinatal outcomes, so neither should be undertaken as a general practice.” Instead, ACOG recommends that tocolytic drugs be used once (probably given intravenously in the hospital) to prolong the pregnancy for two to seven days. This may allow the physician to administer steroids to improve fetal lung maturity and to consider transporting the mother to a tertiary care facility.2

Cochrane Abstract

Background: Some women who have threatened to give birth prematurely subsequently settle. They may then take oral tocolytic maintenance therapy to prevent pre-term birth and to prolong gestation.

Objectives: To assess the effects of oral betamimetic maintenance therapy after threatened preterm labor for preventing preterm birth.

Search Strategy: The authors searched the Cochrane Pregnancy and Childbirth Trials Register (June 2005) and Medline (from 1996 to August 2003).

Selection Criteria: Randomized controlled trials (RCTs) comparing oral betamimetic therapy with alternative tocolytic therapy, placebo, or no therapy for maintenance following treatment of threatened preterm labor.

Data Collection and Analysis: Two review authors independently applied the selection criteria and carried out data extraction and quality assessment of studies.

Primary Results: Eleven randomized controlled trials were included. No differences were seen for admission to the neonatal intensive care unit when betamimetics were compared with placebo (relative risk [RR] = 1.29; 95% confidence interval [CI], 0.64 to 2.60; one RCT of terbutaline [Brethine] with 140 women) or with magnesium (RR = 0.80; 95% CI, 0.43 to 1.46; one RCT of 137 women). The rate of preterm birth (less than 37 weeks' gestation) showed no significant difference in four RCTs, two comparing ritodrine with placebo or no treatment and two comparing terbutaline with placebo or no treatments (RR = 1.08; 95% CI, 0.88 to 1.32; 384 women). No differences between betamimetics and placebo, no treatment, or other tocolytics were seen for perinatal mortality and morbidity outcomes. Some adverse effects such as tachycardia were more frequent in the betamimetics groups than in the groups allocated to placebo, no treatment, or another type of tocolytic.

Reviewers' Conclusions: Available evidence does not support the use of oral betamimetics for maintenance therapy after threatened preterm labor.

These summaries have been derived from Cochrane reviews published in the Cochrane Database of SystematicReviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the originalreviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minorediting changes have been made to the text (http://www.cochrane.org).

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