Human development starts in the prenatal stage when the fetus is within the womb. Cortisol is a human hormone that occurs as a result of stress. A fetus can be effected by cortisol within the mother's system prior to birth. The effects of high levels of cortisol prenatally include slower development in the first year of life.
An infant can also be affected by the cortisol in their system if they have elevated stress levels. If this becomes a regular state the child can result in permanent changes in brain development. Long term this can result in behavioral problems, emotional problems, and lowered intellectual development.