Stressful crowding during pregnancy advances onset of offspring adrenocortical rhythm.

Stress by crowding and disturbance during the final third of pregnancy in mice advanced the onset of the diurnal plasma corticosterone rhythm in the male offspring from day 25 to day 18. Treated pups showed this altered development whether fostered to treated or to control dams, but it was not apparent in control pups raised by treated dams. Graded adrenocortical responses to increasingly stressful stimuli were not affected by stress during gestation.