MATERNAL CORTICOTROPIN-RELEASING HORMONE LEVELS IN THE EARLY 3RD-TRIMESTER PREDICT LENGTH OF GESTATION IN HUMAN-PREGNANCY

OBJECTIVE: Corticotropin releasing hormone, a hypothalamic neuropeptid e, plays a major role in regulating pituitary-adrenal function and the physiologic response to stress. During pregnancy corticotropin-releas ing hormone is synthesized in large amounts by the placenta and releas ed into the maternal and fetal circulations. Various endocrine, autocr ine, and paracrine roles have been suggested for placental corticotrop in-releasing hormone. The aim of this study was to prospectively asses s the relationship between maternal plasma concentrations of corticotr opin-releasing hormone in the early third trimester of pregnancy and t he length of gestation in two groups of deliveries, with and without s pontaneous labor. STUDY DESIGN: In a sample of 63 women with singleton intrauterine pregnancies, maternal plasma samples were collected betw een 28 and 30 weeks' gestation and corticotropin-releasing hormone con centrations were determined by radioimmunoassay. Each pregnancy was da ted on the basis of last menstrual period and early ultrasonography. P arity, antepartum risk conditions, presence or absence of spontaneous labor, and birth outcomes were abstracted from the medical record.RESU LTS: Maternal corticotropin-releasing hormone levels between 28 and 30 weeks' gestation significantly and negatively predicted gestational l ength (P <.01) after adjustment for antepartum risk. Moreover, subject s who were delivered preterm had significantly higher corticotropin-re leasing hormone levels in the early third trimester (P <.01) than did those who were delivered at term. In deliveries preceded by spontaneou s onset of labor, maternal third-trimester corticotropin-releasing hor mone levels significantly and independently predicted earlier onset of labor (P<.01) and preterm labor (P<.05), whereas in deliveries effect ed by induction of labor or cesarean delivery, maternal corticotropin- releasing hormone levels were a marker of antepartum risk but not a st atistically independent predictor of gestational length. CONCLUSION: T hese findings support the premise that placental corticotropin-releasi ng hormone is potentially implicated in the timing of human delivery i n at least two ways. First, placental corticotropin-releasing hormone may play a role in the physiology of parturition. Premature or acceler ated activation of the placental corticotropin-releasing hormone syste m, as reflected by precocious elevation of maternal corticotropin-rele asing hormone levels, may therefore be associated with earlier onset o f spontaneous labor and resultant delivery. Second, placental corticot ropin-releasing hormone may be a marker of antepartum risk for preterm delivery and therefore an indirect predictor of earlier delivery. The implications of these findings are discussed in the context of the ne uroendocrinology of placental corticotropin-releasing hormone and huma n parturition. Furthermore, the role of corticotropin-releasing hormon e as a possible effector of prenatal stress in producing alterations i n the timing of normal delivery is detailed.