Suppression of preterm labour. Current concepts.

Preterm delivery occurs in 5 to 9% of pregnancies and the complications of prematurity account for more than 60% of perinatal mortality. In spite of tocolytic agents being available for over 20 years, and in widespread use, there has been no decrease in the number of preterm births. Many therapeutic agents have been investigated for efficacy and safety in tocolysis, including ethanol, beta 2-adrenoceptor agonists, prostaglandin synthetase inhibitors and calcium channel blockers. While the ability to delay delivery for up to 7 days has been shown, there is little convincing evidence that any further prolongation of pregnancy can be obtained. However, the value in delaying delivery until corticosteroids can be administered has been demonstrated. Problems in diagnosing preterm labour account for much of the difficulty in interpreting the literature, and the conflicting results of clinical trials.