Preterm Labour: Mechanisms and Risks


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.



Anderson ABM, Flint AP and Turnbull AC (1975) Mechanism of action of glucocorticoids in induction of ovine parturition: effect on placental steroid metabolism. Journal of Endocrinology 66: 61–70.

Berridge MJ, Bootman MD and Lipp P (1998) Calcium – a life and death signal. Nature 395: 645–648.

Bocking AD (1998) Preterm labour: recent advances in understanding of pathophysiology, diagnosis and management. Current Opinion in Obstetrics and Gynecology 10: 151–156.

Iams JD, Goldenberg RL, Meis PJ et al. (1996) The length of the cervix and the risk of spontaneous premature delivery. New England Journal of Medicine 334: 567–572.

Keirse MJNC (1995) New perspectives for the effective treatment of preterm labor. American Journal of Obstetrics and Gynecology 173: 618–628.

Liggins GC, Fairclough RJ, Grieves SA, Forster CS and Knox BS (1977) Parturition in the sheep. Ciba Foundation Symposium 47: 5–30.

Mecenas CA, Giussani DA, Owiny JR et al. (1996) Production of premature delivery in pregnant rhesus monkeys by androstenedione infusion. Nature Medicine 2: 443–448.

Miyamura K, Malhotra R, Hoppe HJ et al. (1994) Surfactant proteins A (SP‐A) and D (SP‐D): levels in human amniotic fluid and localization in the fetal membranes. A. Biochimica et Biophysica Acta 1210: 313–307.

Ou C‐W, Chen Z‐Q, Qi S and Lye SJ (1998) Increased expression of the rat myometrial oxytocin receptor messenger ribonucleic acid during labour requires both mechanical and hormonal signals. Biology of Reproduction 59: 1055–1061.

Word RA (1995) Myosin phosphorylation and the control of myometrial contraction/relaxation. Seminars in Perinatology 19: 3–14.

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.

López Bernal A, Europe‐Finner GN, Phaneuf S and Watson SP (1995) Preterm labour: a pharmacological challenge. Trends in Pharmacological Sciences 16: 129–133.

Lu J (1997) Collectins: collectors of microorganisms for the innate immune system. BioEssays 19: 509–518.

Rice GE and Brennecke SP (1993) Preterm labour and delivery. Baillière's Clinical Obstetrics and Gynaecology 7: 477–668.

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.

Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

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