Initiation of Labor

  • Luis A. Cibils
  • Mary Campau Ryerson


The extraordinary hormonal and physical changes that occur in the pregnant subject and her uterus are the ultimate expression of the wonders of adaptation. Pregnancy brings a complete turnabout of the hormonal status of the individual with the appearance of the placenta, a new, large, and potent endocrine organ that secretes a number of new hormones and metabolizes others produced by the patient or her conceptus. In addition, the physical changes of a growing uterus—a potent, contractile, hollow viscus receiving a large proportion of the cardiac output to supply the enlarged vascular bed (IVS)—constitute constant threats to interruption of the growing conceptus. Why pregnancy terminates at a given stage, and what triggers labor are fundamental biologic problems that, so far, have not been solved (an equally monumental problem, possibly closely related, is why the conceptus—a partial homograft—is not rejected by the maternal organism).


Sarcoplasmic Reticulum Fetal Membrane Oxytocin Receptor Spontaneous Labor Uterine Activity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Caldeyro-Barcia R, Poseiro J J: Oxytocin and contractility of the human uterus. Ann NY Acad Sei 75: 813, 1959.CrossRefGoogle Scholar
  2. Caldeyro-Barcia R, Sereno JA: The response of the human uterus to oxytocin throughout pregnancy, in Caldeyro-Barcia R, Heller H (eds): Oxytocin. NY, Pergamon, 1961, pp 177–202.Google Scholar
  3. Challis JRG, Manning FA: Control of par-turition in subhuman primates. Semin Perinatol 2: 247, 1978.PubMedGoogle Scholar
  4. Csapo AI: The onset of labor. Lancet 1: 277, 1961.CrossRefGoogle Scholar
  5. Csapo AI: The prospects of PGs in postcon-ceptional therapy. Prostaglandins 3: 245, 1973.PubMedCrossRefGoogle Scholar
  6. Csapo AI: The “seesaw” theory of the regulatory mechanism of pregnancy. Am J Obstet Gynecol 121: 578, 1975.Google Scholar
  7. Csapo AI, Takeda H: Effect of progesterone on the electric activity and intrauterine pressure of pregnant and parturient rabbits. Am J Obstet Gynecol 91: 221, 1965.PubMedGoogle Scholar
  8. Farr CJ, Robards MF, Theobald GW: Changes in myometrial sensitivity to oxytocin in man during the last six weeks of pregnancy. J Physiol 196: 58, 1968.Google Scholar
  9. Flint APF, Anderson ABM, Patten PT, et al: Control of utero-ovarian venous prostaglandin F during labour in sheep: acute effects of vaginal and cervical stimulation. J Endocrinol 63: 67, 1974.PubMedCrossRefGoogle Scholar
  10. Garfield RE, Rabideau S, Challis JRG, et al: Ultrastructural basis for maintenance and termination of pregnancy. Am J Obstet Gynecol 133: 308, 1979.PubMedGoogle Scholar
  11. Kuriyama H, Csapo AI: Placenta and myometrial block. Am J Obstet Gynecol 82: 592, 1961.PubMedGoogle Scholar
  12. Liggins GC: Premature parturition after in-fusion of coritcotropin or Cortisol into fetal lambs. J Endocrinol 42: 323, 1968.PubMedCrossRefGoogle Scholar
  13. Liggins GC, Fairclogh RJ, Grieves SA, et al: The mechanism of initiation of parturition in the ewe. Recent Prog Horm Res 29: 111, 1973.Google Scholar
  14. Liggins GC, Kennedy PC, Holm LW: Failure of initiation of parturition after electrocoagulation of the pituitary of the fetal lamb. Am J Obstet Gynecol 98: 1080, 1967.PubMedGoogle Scholar
  15. MacDonald PC, Porter JC, Schwarz BE, et al: Initiation of parturition in the human female. Semin Perinatol 2: 273, 1978.PubMedGoogle Scholar
  16. Theobald GW, Robards MF, Suter PEN: Changes in myometrial sensitivity to oxytocin in man during the last six weeks of pregnancy. J Obstet Gynaecol Br Comwlth 76: 385, 1969.CrossRefGoogle Scholar
  17. Thorburn GD: Hormonal control of parturition in the sheep and goat. Semin Perinatol 2: 235, 1978.PubMedGoogle Scholar

Copyright information

© John Wright PSG · Inc. 1981

Authors and Affiliations

  • Luis A. Cibils
    • 1
  • Mary Campau Ryerson
    • 1
  1. 1.Department of Obstetrics and Gynecology The Chicago Lying-In HospitalThe University of ChicagoUSA

Personalised recommendations