The Discovery of Different Types of Cervical Mucus and the Billings Ovulation Method

Erik Odeblad
Reproduced with Permission


  1. Abstract
  2. Introduction
  3. Anatomy and Physiology
  4. What is Mucus?
  5. The Commencement of my Research
  6. The Existence of Different Types of Crypts and of Mucus
  7. Identification and Description of G, L, and S Mucus
  8. G- and G+ Mucus
  9. Age, Pregnancy, the Pill and Microsurgery
  10. P Mucus
  11. F Mucus
  12. The Role of the Vagina
  13. The Different Types of Secretions and the Billings Ovulation Method
  14. Early Infertile Days
  15. The Days of Possible Fertility
  16. Late Infertile Days
  17. Anovulatory Cycles
  18. Lactation
  19. Diseases and the Billings Ovulation Method
  20. The Future
  21. Acknowledgements
  22. Author's Note
  23. References
  24. Appendix


An introduction to and some new anatomical and physiological aspects of the cervix and vagina are presented and also an explanation of the biosynthesis and molecular structure of mucus.

The history of my discoveries of the different types of cervical mucus is given. In considering my microbiological investigations I suspected the existence of different types of crypts and cervical mucus and in 1959 I proved the existence of these different types.

The method of examining viscosity by nuclear magnetic resonance was applied to microsamples of mucus extracted outside of several crypts. Preliminary studies in 1966 proved the existence of two types and in 1977 the three types G, L, and S mucus were described. Sperm cells were transported in Smucus, L mucus attracted malformed sperm and G mucus formed a plug in the cervical canal in the infertile phases.

In 1990 a new mucus, P mucus, was characterized. A mucolytic enzyme, probably emanating from the isthmus of the cervix, was associated with this mucus and facilitated the upward movement of sperm cells. At the end of 1993 another mucus, F mucus, was identified. This mucus is probably produced by fetal cells remaining in the wall of the neck of the uterus.

Variations in these different types of mucus throughout life and during the course of a cycle, and their importance for the Billings Ovulation Method, are presented and discussed.


I am very pleased to present my research on the different types of secretion from the neck of the uterus [cervix] and their relationship with the Billings Ovulation Method (Billings et al. 1972; Billings 1983; Billings and Westmore 1992).

The principal indication of fertile days in a menstrual cycle is the appearance and the sensation of a wet substance [mucus] emanating from the epithelial membrane of the cervix. 'Ibis sign precedes ovulation and depends upon the growth in the ovary of a follicle which produces oestrogens and which is usually succeeded by the rupture and the release of an ovum (ovulation). The last day on which this substance with fertile characteristics is observed is called the Peak day. This day is also the day of ovulation in 80% of cycles. Ovulation occurs on the preceding day in about 10% of cycles and in about 10% of cycles on the day following the Peak.

Besides the cervical secretion there is also a maturation and cellular sloughing (of superficial squamous cells) of the vagina. There are also some contributions emanating from the isthmus, the endometrium and the tubes. It has also been demonstrated that peritoneal fluid and, during ovulation, follicular fluid contribute to the cervical flow.

Usually, in the infertile phases, vaginal fluids are reabsorbed by the pockets of Shaw (vaginal recesses), situated in the lower part of the vagina (Odeblad 1964), and the element manganese plays a role in this process (Rudolfsson and Odeblad 1971). The preovulatory epithelial proliferation lessens the reabsorption and the flow outside the vagina increases and, as a consequence, facilitates the wet, slippery sensation in the fertile phase.

Since the beginning of the 20th century it has been known that the ovarian cycle causes variations in the secretions of the mucous membrane of the cervix. References to that work are found in Billings (1983). &t that time it was generally supposed that the secretion of the glands (or crypts) of the cervix changed in a manner more to synchronize with the course of the cycle. I wish to report that the directives or rules elaborated by Drs John and Evelyn Billings have not been influenced by my research. Those rules are always valid.

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