Study of the profiles of prolactin and other hormones in both maternal plasma and amniotic fluid during labor

Abstract

The effects of a dopamine antagonist and stress of labor on prolactin (PRL) concentrations were studied in maternal plasma and amniotic fluid during term delivery. In procedure 1, maternal blood and amniotic fluid samples were obtained from 5 normal full-term deliveries at 20-minute intervals for 180 minutes after the intravenous bolus of 10 mg metoclopramide (MCP) during labor just before delivery. Amniotic fluid samples were drawn through a transcervical intrauterine pressure catheter to avoid contamination with maternal blood. PRL, 17 beta-estradiol (E2), progesterone (P) and cortisol were measured by means of radioimmunoassay (RIA), and free MCP concentrations were measured by high pressure liquid chromatography. In procedure 2, maternal blood and amniotic fluid samples were obtained from 12 full-term pregnancies with spontaneous delivery and 10 cases of elective cesarean section when birth was imminent. The amniotic fluid was obtained by direct sampling from the forewaters in spontaneous delivery and by means of a syringe inserted through amniotic membrane after the uterine wall had been incised in cesarean section. PRL, beta-endorphin (beta-EP) and cortisol were measured by RIA. The PRL levels in maternal plasma increased significantly (p less than 0.01) after the MCP injection. The peak value of PRL net increase (delta PRL) was 676.5 +/- 189.6 ng/ml. However, the PRL levels in amniotic fluid did not change significantly after the administration of this drug. Although the delta PRL levels in maternal plasma were significantly (p less than 0.001) correlated with MCP concentrations (r = 0.812) after the MCP injection, there was no correlation between delta PRL and MCP concentrations in amniotic fluid. No significant changes in E2, P and cortisol levels in both samples were observed after the MCP injection. The plasma PRL levels in vaginal delivery cases were significantly (p less than 0.05) lower than those in elective cesarean section cases (123.3 +/- 15.8 ng/ml vs. 181.0 +/- 22.2 ng/ml), and the plasma beta-EP and cortisol levels in vaginal delivery cases were significantly (p less than 0.01, p less than 0.001) higher than those in elective cesarean section cases respectively (beta-EP: 134.8 +/- 25.6 pg/ml vs. 49.7 +/- 12.3 pg/ml, cortisol: 79.4 +/- 5.8 micrograms/dl vs. 30.2 +/- 3.3 micrograms/dl). Therefore, a significant reduction in plasma PRL levels was accompanied by a marked rise in plasma beta-EP and cortisol levels during labor. In amniotic fluid, however, there were no significant differences of PRL, beta-EP and cortisol levels in vaginal delivery cases and elective cesarean cases.(ABSTRACT TRUNCATED AT 400 WORDS)