Pharmacology of tocolytic agents

Area of Science:

• Obstetrics and Gynecology
• Perinatology
• Pharmacology

Background:

• Preterm labor is a significant concern in obstetrics.
• Selective beta-receptor agonists have been widely used to inhibit preterm labor for over a decade.
• While overall preterm delivery rates remain unchanged in many regions, the impact on very preterm births is of greater clinical interest.

Purpose of the Study:

• To evaluate the efficacy of beta-receptor agonists in inhibiting preterm labor.
• To assess the impact of beta-receptor agonist therapy on fetal outcomes, specifically focusing on very preterm deliveries and low birth weight infants.
• To examine the safety profile and necessity of careful monitoring during treatment.

Main Methods:

• Review of controlled studies on beta-receptor agonists for preterm labor inhibition.
• Analysis of pregnancy prolongation and fetal outcome data.
• Examination of Swedish national data on preterm deliveries, birth weights, and perinatal mortality rates before and after the introduction of beta-receptor agonist therapy.

Main Results:

• Controlled studies demonstrate significant pregnancy prolongation and improved fetal outcomes with beta-receptor agonists.
• Despite unchanged overall preterm delivery rates, Sweden saw a significant decrease in deliveries before week 32 and infants with birth weight <1500g after introducing this therapy.
• Perinatal mortality in Sweden decreased from 60% in 1973 to 40% in 1980, potentially influenced by labor inhibition therapy.

Conclusions:

• Beta-receptor agonists are beneficial for selected patients in inhibiting preterm labor, leading to improved fetal outcomes.
• High doses necessitate careful maternal and infant monitoring due to potential side effects.
• The therapy may have contributed to the observed decrease in very preterm births, low birth weights, and perinatal mortality in Sweden.