Prolactin and certain obstetric stress conditions.

Prolactin levels were evaluated during certain stress conditions, obstetric or gynecologic surgical interventions, labor, and birth. In 68 patients undergoing voluntary abortion, prolactin levels were measured to study the effect of anesthetics and of dilatation and curettage on hormonal secretion. Prolactin levels were evaluated in five patients undergoing elective cesarean section and in five post-menopausal patients undergoing total abdominal hysterectomy with bilateral oophorectomy. Moreover, prolactin concentration in serial samples of blood was estimated in 32 normal patients with spontaneous vaginal delivery at term and in 16 newborns at term after 30-60 and 120 min following birth. Prolactin responsiveness to TRH was evaluated in 12 newborns at the 4th day of life. Plasma prolactin levels rose in all the stress conditions investigated except in labor, during which hormone levels showed a decrease starting 2 h before delivery and reaching the lowest value 1 h prior. From this moment on there was a remarkable rise in prolactin concentration, with a peak 1 h after delivery. The decrease in prolactin levels during labor could possibly be due to an increase in dopaminergic activity. Moreover, the finding of no variation of prolactin levels during induced abortion in a group of patients pretreated with methysergide supports the view that the serotoninergic system also affects prolactin release.