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. 1995 May;1(5):460-3.
doi: 10.1038/nm0595-460.

A placental clock controlling the length of human pregnancy

M McLean  1 , A Bisits, J Davies, R Woods, P Lowry, R Smith
Affiliations

A placental clock controlling the length of human pregnancy

M McLean et al. Nat Med. 1995 May.

Abstract

We report the existence of a 'placental clock', which is active from an early stage in human pregnancy and determines the length of gestation and the timing of parturition and delivery. Using a prospective, longitudinal cohort study of 485 pregnant women we have demonstrated that placental secretion of corticotropin-releasing hormone (CRH) is a marker of this process and that measurement of the maternal plasma CRH concentration as early as 16-20 weeks of gestation identifies groups of women who are destined to experience normal term, preterm or post-term delivery. Further, we report that the exponential rise in maternal plasma CRH concentrations with advancing pregnancy is associated with a concomitant fall in concentrations of the specific CRH binding protein in late pregnancy, leading to a rapid increase in circulating levels of bioavailable CRH at a time that coincides with the onset of parturition, suggesting that CRH may act directly as a trigger for parturition in humans.

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