Prepartum maturation of the lung in fetal sheep: relation to cortisol

We studied the relationship of certain fetal and maternal hormones to indicators of lung maturation in 12 fetal lambs delivered at gestational ages (GA) of 123-149 days. Maternal estrogen, maternal progesterone, and fetal prolactin did not correlate with GA or the indicators of fetal lung maturation. Fetal cortisol (range 4-165 ng X ml-1) increased with advancing GA (r = 0.747, P less than 0.01). All of the following showed a wide range of late gestation and showed a significant positive correlation with fetal cortisol: lung volumes at 40 cmH2O and 10 cmH2O on the deflation during air pressure-volume studies; saturated phosphatidylcholine (SPC) in lung tissue and in lavage fluid expressed both as mg X g-1 of wet lung and as percent of total phospholipids (%PL); total SPC (lung tissue plus lavage fluid): and SPC in lavage fluid as percent of total SPC. Lung DNA correlated inversely with GA and cortisol. All variables (except lavage fluid SPC as %PL) correlated more closely with cortisol than GA. Morphological development of lung was also related more closely to cortisol than GA. These results suggest that functional lung maturity is attained late in gestation and that endogenous cortisol is an important physiological factor in control of fetal lung maturation.