Factors implicated in the initiation of human parturition in term and preterm labor: a review

Abstract

After accommodating the pregnancy for an average of 40 weeks, the uterus expels the fetus, the placenta and the membranes through the birth canal in a process named parturition. The absolute sequence of events that trigger and sustain human parturition are not yet fully clarified. Evidence suggests that spontaneous preterm and term labor seem to share a common inflammatory pathway. However, there are several other factors being involved in the initiation of human parturition. Placental corticotropin releasing hormone production seems to serve as a placental clock that might be set to ring earlier or later determining the duration of pregnancy and timing of labor. Estrogens do not cause contractions but their properties seem to capacitate uterus to coordinate and enhance contractions. Cytokines, prostaglandins, nitric oxide and steroids seem also to induce ripening by mediating remodeling of the extracellular matrix and collagen. Infection and microbe invasion resulting in chorioamnionitis also represents a common cause of early preterm labour. This review provides an overview of all these factors considered to be implicated in the initiation of human parturition.

Chinese abstract

在调节平均40周的妊娠后,子宫通过产道排出胎儿，胎盘和胎膜的过程称为分娩。触发和维持人类分娩的绝对事件序列仍未完全阐明。有证据表明，自发早产和足月产似乎都遵循一条同样的炎症通路。然而，仍有一些其他的因素与人类分娩的触发有关。胎盘促肾上腺激素释放激素的产生似乎充当胎盘时钟的作用，时钟响的时间可能会设定的早或晚，决定了孕期的时长和分娩的时间。雌激素并不造成宫缩，但是它的性质可使子宫协调而加强宫缩。细胞因子、前列腺素、一氧化氮和类固醇似乎通过重塑细胞外基质和胶原来同样促进成熟。感染和微生物入侵所导致的绒毛膜羊膜炎也是常见的早产原因之一。这篇综述提供了与人类分娩的相关因素的概述。

• Androgens
• estrogens
• hypothalamus
• pregnancy

Declaration of interest

The authors declare that there is no conflict of interest.