MATERNAL PROLACTIN SECRETION IS PHASIC DURING INDUCED TERM AND POSTTERM LABOR

OBJECTIVE: We hypothesized that regimens of labor induction do not alt er the biphasic secretion of maternal prolactin (PRL) seen during spon taneous labor. METHODS: Serial blood samples drawn from 12 women befor e, during, and after induced labor were assayed for PRL and hCG and co mpared with cervical dilatation and uterine contraction frequency (UCF ). Induction methods were cervical ripening with dinoprostone gel (Pre pidil) followed by oxytocin infusion (n = 1), amniotomy followed by ox ytocin (n = 4), oxytocin followed by amniotomy (n = 3), amniotomy only (n = 2), and oxytocin only (n = 2). RESULTS: Regardless of the induct ion method, PRL decreased with advancing cervical dilatation during th e first stage of labor and reached a nadir at full dilatation. Prolact in levels then increased rapidly during the second stage, correlating significantly with the increase in UCF, and peaked at 1 hour postpartu m before decreasing. Levels of hCG increased during labor and peaked j ust before or at delivery before rapidly decreasing. CONCLUSIONS: The biphasic secretion of maternal PRL is a fundamental characteristic of active term labor and occur regardless of the method used to induce la bor. Copyright (C) 1997 by the Society for Gynecologic Investigation.