Preterm Labour: Mechanisms and Risks

Abstract

Preterm labour (the occurrence of labour before 37 completed weeks of pregnancy) complicates millions of pregnancies throughout the world and accounts for a disproportionately high percentage of perinatal deaths and long‐term handicap of the surviving infants. Research efforts must focus on the prediction and accurate diagnosis of this condition and the development of better, more selective, therapy.

Keywords: preterm labour; myometrium; uterine contractility; second messengers; tocolysis

Figure 1.

Regulation of contractility in myometrial cells. Stimulatory agonists bind to seven‐transmembrane‐domain receptors coupled to heterotrimeric (α, β, γ) G proteins. Activation of phospholipase C (PLC) generates the second messenger inositol 1,4,5‐triphosphate (IP3) which releases Ca2+ from internal stores. Ca2+ also enters the cells through voltage‐operated membrane channels (not shown). The enzyme myosin light‐chain kinase (MLCK) is activated by Ca2+ and phosphorylates myosin light chains (MLC20), leading to contraction. When the level of Ca2+ decreases, MLC20 is dephosphorylated and the muscle relaxes. Small guanosine triphosphate (GTP)‐binding proteins such as Rho can sustain contractions: Rho‐activated kinase phosphorylates MLC20 and inhibits myosin phosphatase. This pathway enhances contractility in a Ca2+‐independent manner. GDI (guanosine diphosphate (GDP) dissociation inhibitor) is an inhibitory guanosine diphosphateGDP/GTP exchange protein.

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Further Reading

Elder MG, Lamont RF and Romero R (1997) Preterm Labor. New York: Churchill Livingstone.

Keith L and Papiernik E (1998) Multiple gestation. Clinical Obstetrics and Gynecology 41: 1–139.

Lefkowitz RJ (1998) G protein‐coupled receptors. III. New roles for receptor kinases and β‐arrestin in receptor signaling and desensitization. Journal of Biological Chemistry 273: 18677–18680.

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Sanborn BM, Yue C, Wang W and Dodge KL (1998) G protein signalling pathways in myometrium: affecting the balance between contraction and relaxation. Reviews of Reproduction 3: 196–205.

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Bernal, Andrés López(Apr 2001) Preterm Labour: Mechanisms and Risks. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0002141]