Plasma CRH levels at 16-20 weeks do not predict preterm delivery in women at high-risk for preterm delivery

Abstract

Corticotropin releasing hormone (CRH) levels have been identified in a general population as a marker for gestational length, with low levels associated with prolonged gestation and elevated levels associated with preterm delivery. The objective was to examine the utility of second-trimester plasma CRH measurement as a marker for preterm delivery in women at high risk for preterm delivery. A secondary analysis of data from a multicenter placebo-controlled trial to evaluate 17 α hydroxyprogesterone caproate (17P) in the prevention of recurrent preterm birth. Women with a history of a previous preterm birth at <37 wks were enrolled (16-20 wks) and randomly assigned in a 2 to 1 ratio to weekly injections of 17P or matching placebo. Of 463 women enrolled in the trial, plasma CRH was obtained prior to treatment in 169 patients (113 assigned 17-P, 56 placebo). Plasma levels of CRH were compared between those who delivered preterm and those delivering at term. Data were analyzed using the Wilcoxon Rank Sum test. Our sample size had 99% power to detect a 0.1 ng/mL difference in CRH for delivery <37 wks overall, and 80% power to detect a similar difference among placebo. CRH levels (mean ± SD) were similar between those delivering <37 and those delivering ≥37 wks (0.41 ± 0.12 ng/mL vs. 0.38 ± 0.12 ng/mL, P = .11), and those delivered at <35 or ≥35 wks (0.39 ± 0.12 vs. 0.40 ± 0.12, P = .68). There were no differences in CRH levels among those in the placebo group who delivered at <37 or ≥37 wks (0.42 ± 0.11 vs. 0.42 ± 0.17, P = .91) or at <35 wks (0.39 ± 0.11 vs. 0.43 ± 0.15, P = .34). There were no differences in baseline CRH levels between those assigned 17P and those assigned placebo (0.38 ± 0.11 ng/mL vs. 0.42 ± 0.14 ng/mL). The overall rates of preterm birth in this cohort of 169 patients were 35.5% at < 37 wks (31.9% 17P, 42.9% placebo), and 18.9% at <35 wks (18.6% vs. 19.6%). A single measurement of CRH at 16-20 wks gestation does not predict recurrent preterm delivery in high risk women with a prior preterm birth.