Value of maintenance therapy with oral tocolytics: a systematic review

The objective was to perform a systematic review of prospective randomized trials evaluating the efficacy of oral tocolytics in the prevention of recurrent preterm labor and its associated complications.

A MEDLINE search of English language articles published since 1966 was performed to identify studies of maintenance oral tocolytic therapy. Studies were included in the review which: 1) randomized patients to an oral tocolytic after stabilization with parenteral therapy; 2) reported results for either a placebo or a control group; and 3) included patients with intact membranes only. These studies were analyzed for nine outcomes, including incidence of preterm delivery, incidence of recurrent preterm labor, latency from treatment to delivery, gestational age, birthweight, admission to an intensive care nursery (ICN), incidence of respiratory distress syndrome (RDS), incidence of intraventricular hemorrhage (IVH), and perinatal mortality.

Seven studies met the inclusion criteria, four of which used oral terbutaline for the treatment arm (two had a control group, and two had a placebo group), and one used oral ritodrine (with a placebo group). Of the remaining two, one used oral ritodrine and oral magnesium chloride (with a control group), and the other used oral terbutaline and oral magnesium chloride (with a placebo group). The results of the individual studies suggest that there was no beneficial effect of oral tocolytic therapy on the incidence of preterm delivery (odds ratio (OR) range: 0.7-2.0), incidence of preterm labor recurrence (OR range: 0.6-3.2), ICN admission (OR range: 1.3-2.0), incidence of RDS (OR range 0.1-4.3), incidence of IVH (OR range 0.3-2.0), perinatal mortality (OR range: 1.6-4.3), or gestational age at delivery.

We concluded that a meta-analysis based on the available studies is not possible due to the fact that there is little that these seven studies have in common with respect to treatment comparisons. In addition, inconsistent definitions of outcome variables makes pooling this data inappropriate and invalid. Therefore, well-designed, large, randomized trials are needed to evaluate the efficacy of oral tocolytics in improving perinatal outcome.