Maternal behavior of dams treated with ACTH during pregnancy

Experimental female rats were injected with ACTH during the last third of their pregnancy. This treatment resulted in prolongation of gestation and in abnormal development of the young. The number of resorptions, stillbirths, and congenitally malformed pups was increased and those that appeared normal had lower body weights. The experimental treatment also severely affected the ability of the dams to exhibit normal maternal behavior. Significant individual differences were noted in the sensitivity of the dams to the experimental treatment. Cross-fostering experiments revealed that experimental dams exhibited normal maternal behavior towards control foster pups, after an initial delay of 24 h. When experimental pups, born after a prolonged gestation, or delivered by caesarian section after the normal duration of gestation, were given to control mothers, normal maternal behavior was observed, but the survival rate of the young was not increased.