Ovarian and placental hormones during prolactin suppression and stimulation in early human pregnancy.

Twenty-seven healthy females referred for legal abortion between the sixth and ninth week of pregnancy were treated for 1 week with either bromocriptine, metoclopramide or placebo. Serum prolactin was significantly (P < 0.01) elevated by metoclopramide and suppressed by bromocriptine. Despite a more than tenfold difference in circulating prolactin levels among these two groups, no significant difference was found in serum levels of progesterone, oestradiol, human chorionic gonadotrophin (hCG) human placental lactogen (hPL) or pregnancy specific B1-glycoprotein (SP1). These data suggest that circulating levels of prolactin below 150 ng/ml are without effect on either luteal or placental hormone secretion during early human pregnancy.