Observations of the resistance of the human cervix to surgical dilation

Anthony, George Strathie (1983) Observations of the resistance of the human cervix to surgical dilation. MD thesis, University of Glasgow.

Abstract

The thesis begins with a historical review of dilatation of the cervix and then considers the anatomical and physiological properties of the cervix which affect its physical properties. The ease with which the cervix can be dilated is determined by the diameter of the cervical canal prior to dilatation and by the compliance of the cervical tissue. The diameter of the cervix is influenced by the number of pregnancies which the patient has had. The compliance of cervical tissue is affected by the complex changes which take place in the collagen fibre matrix and ground substance of the cervical stroma. A review of the complications of first trimester termination of pregnancy has shown that the earlier a pregnancy is terminated, the less likely the patient is to have complications. The cervix may sustain damage during dilatation of the cervix, which may compromise her future reproductive capacity. Attention is then turned to the problem of cervical incompetence. The history of this condition is reviewed and a discussion of the aids to diagnosis is presented. The original work described in the thesis hinges on measurements of the force applied during surgical dilatation of the cervix. These measurements were made using an instrument which was developed by the author and his associates, specifically for the purpose of the studies here presented. The factors which influence the passage of a dilator through the cervix are discussed. Measurement of the force required to dilate a cervix from 3 mm to 8 mm which was defined as the Cervical Resistance Index (CRI), takes account of many of these variable factors. Measurement of Cervical Resistance Index was performed on a total of 590 patients in 3 groups:- 1. 200 non-pregnant patients. 2. 355 pregnant patients undergoing first trimester termination of pregnancy. 3. 35 patients with a history of previous spontaneous mid-trimester abortion. The study of non-pregnant patients was undertaken to establish baseline values of cervical resistance. The influence of parity, hormone status contraception and the stage of the menstrual cycle on CRI is presented. Increasing parity significantly reduces CRI. Postmenopausal women show significantly higher CRI than pre-menopausal women, while patients using Depo-Provera for contraception have significantly lower CRI than normal cycling women. The study of pregnant patients undergoing termination of pregnancy was performed in order to evaluate the use of four hormones (oestradiol, progesterone, medroxy-progesterone acetate and prostaglandin E2) in bringing about changes in cervical compliance. All these substances are thought to play a role in the biological control of cervical softening in late pregnancy. An increase in cervical compliance makes the cervix easier to dilate and thus reduces the likelihood of damage being sustained during dilatation. Such damage has been shown to compromise a patient's future reproductive capacity. Prostaglandin E2 was shown to significantly reduce the cervical resistance index in multiparous patients. In nulliparous patients, this hormone did not have the consistent effect on CRI seen in multiparous patients. Since nulliparous patients are more likely than multiparous patients to suffer damage to the cervix during dilatation, further research should concentrate on making termination of pregnancy safer for these women. A study to measure cervical resistance index in patients with a history of spontaneous mid-trimester abortions is then described. This study was undertaken to evaluate the use of this technique in assisting in the diagnosis of cervical incompetence. The study identified patients with abnormally low CRI. The number of these patients who have subsequently conceived is small but knowledge of the CRI has allowed a more rational management and consequently improved obstetric performance.

• Item Type: Thesis (MD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Andrew Calder
• Keywords: Obstetrics, Medicine
• Date of Award: 1983
• Depositing User: Enlighten Team
• Unique ID: glathesis:1983-72268
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 May 2019 15:12
• Last Modified: 24 May 2019 15:12
• URI: https://theses.gla.ac.uk/id/eprint/72268