Objective: The objective was to investigate whether the addition of thyrotropin-releasing hormone to antepartum betamethasone further reduces the incidence of respiratory disease in preterm infants.
Study design: A randomized, placebo-controlled, double-blind trial of antepartum thyrotropin-releasing hormone (400 micrograms given intravenously four times) and betamethasone (5 mg given intramuscularly four times) was conducted in 378 mothers likely to be delivered between 24 and 32.6 weeks' gestation. Statistical analysis was by relative risk, chi 2, t tests, and multiple logistic regression analysis.
Results: Four hundred five live-born infants were delivered. In infants without lethal abnormalities delivered between 24 hours and 10 days from entry (n = 175) the incidence of respiratory distress syndrome was reduced from 52% to 31% (relative risk 0.61, 95% confidence interval 0.41 to 0.89) and that of severe respiratory distress syndrome from 42% to 20% (relative risk 0.48, 95% confidence interval 0.29 to 0.78) in the placebo and thyrotropin-releasing hormone groups, respectively. The number of deaths fell from 14 to one (relative risk 0.08, 95% confidence interval 0.01 to 0.63). The incidence of chronic lung disease was not significantly different, but that of an adverse outcome (chronic lung disease or death by 36 weeks' gestation) fell from 29% in the placebo group to 16% with thyrotropin-releasing hormone (relative risk 0.55, 95% confidence interval 0.31 to 0.99).
Conclusion: The addition of thyrotropin-releasing hormone to antepartum glucocorticoid treatment reduces the incidence of respiratory distress syndrome and improves survival in preterm infants.