Lung tissue progesterone in the human fetus and neonate

During fetal life human lungs have a high progesterone concentration (average 380 ng/g at 14 weeks of gestation and 635 ng/g at 32 weeks). At 30 h of age, this concentration had decreased to 185 ng/g. During the first 72 h of life, some infants with respiratory distress syndrome (RDS) had a higher amount of progesterone in their lungs than infants with diseases other than RDS. In newborns with RDS, serum transcortin (binding progesterone) was close to the normal value, but serum progesterone concentration 57% below normal. The hypothesis that, in addition to surfactant, lung tissue smooth muscle (regulated among other things by progesterone and prostaglandins) may control lung function at birth is strengthened by the fact that RDS can be provoked by progesterone in the rabbit and that fatty acids and prostaglandins are abnormal in human RDS.