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

Cimetidine, an H2 receptor antagonist, is a potent stimulant of PRL secretion in normal women. In the present study, the PRL response to cimetidine was studied in 34 normal pregnant women and their fetuses during labor. Serum maternal PRL levels increased significantly after the acute iv injection of 400 mg cimetidine 30-45 min before delivery (10 women) as compared to 7 control women given saline. However, PRL levels in serum of umbilical vein and artery did not increase. Similar results concerning PRL levels in umbilical vein and artery serum were obtained when cimetidine was injected 10-20 min (8 women), 60-75 min (8 women) and 90-120 min (8 women) before delivery. It is suggested that fetal pituitary lactotrops are not responsive to cimetidine stimulation.