Effect of metoclopramide on maternal and fetal prolactin secretion during labor.

The effect of acute and chronic maternal administration of metoclopramide on prolactin levels in serum of umbilical vein and artery was investigated in 30 women with normal term pregnancy during labor. Serum maternal prolactin increased significantly when 20 mg metoclopramide was given intravenously 30 to 45 minutes before vaginal delivery. Prolactin values in serum of umbilical vessels did not change as compared with control values when metoclopramide was given to the mother either as a 20-mg intravenous bolus injection or per os for the last 4 days of pregnancy until delivery. Oral administration of metoclopramide in late pregnancy evoked a significant increase in maternal serum prolactin levels. It is suggested that, in humans, therapeutic doses of metoclopramide administered to the mother in late pregnancy stimulate maternal, but not fetal, prolactin secretion.