The most effective interventions for optimizing the neonatal outcome in preterm births are tocolysis and antenatal glucocorticoid treatments, but their value is limited when women present with advanced cervical dilatation. Recent evidence suggesting a rapid rise in maternal corticotropin-releasing hormone (CRH) prompted this study, which was aimed at learning whether midtrimester levels are significantly elevated in a Chinese population when women deliver before 34 weeks’ gestation. Venous blood levels of CRH were estimated by radioimmunoassay in 1014 low-risk women enrolled at 15 to 20 weeks’ gestation. Assay results were obtained by investigators who had no knowledge of the obstetrical outcome. The parturients, whose average age was 31 years, were at 18 weeks’ gestation on average when sampled.Sixty-four women, 6.3 percent of the series, delivered preterm. Forty delivered spontaneously, whereas 24 had labor induced for obstetrical reasons. Plasma CRH levels increased with advancing gestation. When corrected for gestational age and expressed as multiples of the median (MoM) for normal term pregnancies at the same gestational age, values were 1.32 MoM for spontaneously preterm births, 1.07 for iatrogenic preterm births, 1.00 for term deliveries, and 0.7 for postterm deliveries. The spontaneous preterm group had significantly higher levels than the postterm group. The best cutoff for predicting delivery before 34 weeks was 1.9 MoM. Its sensitivity and specificity were 73 and 78 percent, respectively, and its positive and negative predictive values were 4 and nearly 100 percent, respectively. The relative risk of delivering before 34 weeks with a cutoff of 1.9 MoM was 9.4.These findings are consistent with reports on mainly white study populations and support the idea that some placental process taking place as early as midtrimester influences the length of gestation. Plasma CRH, however, had low predictive power in this low-risk group.Br J Obstet Gynaecol 1999;106:1041–1046
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