Postnatal effects of maternal hypercortisonism on skeletal development in newborn rats

Pregnant rats were treated daily by im injections of 10 mg cortisone acetate, on days 8–20 of gestation. Experimental term offspring were smaller than controls. Their long bones were smaller, but contained a higher per cent of ash, calcium, and phosphorus. Sections of the long bones revealed a thinner layer of maturing and calcifying cartilage in the epiphyses, and persistence of bone trabeculae and islets of cartilage, with reduced volume of bone marrow, in the diaphyses. During the first 2 postnatal weeks the experimental offspring gradually reached the control weight. Concomitantly there was a complete disappearance of the bone injuries, and a decrease of the ash and mineral concentration to control levels. It thus appears that cortisone acetate, after passing through the placenta, does not cause true congenital skeletal anomalies, but produces only a transient direct effect on the fetal skeleton.