Maternal prolactin, cortisol, growth hormone and noradrenalin profiles during labor and following delivery.

Maternal prolactin, cortisol, growth hormone and noradrenalin levels were measured immediately before induced labor, during the expulsion stage and 60-90 min following delivery in 10 normal subjects between 38 and 41 wk of gestation. A significant reduction in prolactin levels was accompanied by a marked rise in cortisol and noradrenalin levels, indicating a paradoxical suppression of prolactin due to stress of labor. Growth hormone levels declined both during labor and following delivery, presumably as a result of anti-insulin actions of cortisol and noradrenalin.