Transplacental stimulation of functional and morphologic fetal rabbit lung maturation: effect of thyrotropin-releasing hormone.

We investigated the effect of maternally administered thyrotropin-releasing hormone on functional and morphologic fetal lung maturation. Thyrotropin-releasing hormone (40 micrograms/kg/day) or the vehicle was injected intravenously into the New Zealand White rabbit does on days 25, 26, and 27 of gestation. On day 27 of pregnancy, the does were killed and the fetuses were delivered. The functional pulmonary maturity was assessed by pressure-volume hysteresis while morphologic maturity was assessed by histologic techniques. Enhanced functional and morphologic fetal lung maturation was noted in animals treated with thyrotropin-releasing hormone when compared with controls. An important role of thyrotropin-releasing hormone in fetal lung maturation is proposed.