Uterine contractions

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Uterine contractions are a prerequisite for vaginal delivery. Unless there are mechanical difficulties such as disproportion or malposition, efficient contractions and the expulsive efforts of the mother should result in unassisted vaginal delivery. In most centres, uterine contractions are assessed by external palpation at regular intervals, and the clinical outcome with such practice is generally satisfactory. Dysfunctional labour has been estimated to affect up to 21% of primigravid labours [1]. It is the commonest cause of emergency caesarean sections and hence a significant health and economic issue [2]. Much research has been devoted to the identification of better methods of measuring uterine activity, but the appropriate use of this technology is difficult to define. This chapter discusses the molecular mechanisms involved in uterine contractions, methods used to measure uterine contractions, their reliability and uterine activity in normal, augmented and induced labour and in women with a caesarean scar. Myometrium is predominantly a phasic muscle, although it can exhibit tonic contractions when exposed to high concentration of contractants [3]. Uterine contractions are a direct consequence of the underlying electrical activity in the myometrial cells. The action potentials in uterine smooth muscle result from voltage and time-dependent changes in membrane ionic permeability [4]. Phosphorylation of Serine-19 on the light chain of myosin brings about a significant interaction between myosin and actin in the uterus. This phosphorylation is by myosin light chain kinase activated by calcium channels binding to calmodulin.

Original languageEnglish
Title of host publicationBest Practice in Labour and Delivery
PublisherCambridge University Press
Number of pages12
ISBN (Electronic)9780511635489
ISBN (Print)9780521720687
Publication statusPublished - 1 Jan 2009


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