This paper was presented by Dra Micaela Menarguez at the conference entitled The ‘Billings Revolution’ 70 years later: from fertility knowledge to personalized medicine held in Rome, Italy, April 2023.

The Biology of the Cervix
The cervix is an intricate system of crypts, previously referred to as “cervical glands” (Odeblad, 1972). The anatomical structures of the cervix, which indicate the place where each kind of mucus is located, were studied in detail by Odeblad.

Thus, Odeblad (1997) describes that the crypts producing type G mucus are found at the beginning of the cervix, near to its union with the vagina, a logical place to produce this protective stopper, characteristic of the phases of infertility. Producers of types L and S are found in the intermediate area of the cervix, and those of type P mucus preferably at the end, quite near the uterine body, which facilitates its function.

Cervical epithelium contains receptors for estradiol and progesterone, which is why we know that the cervix is a “target organ” for these hormones.

At the moment of secretion, the cellular membrane breaks, producing the liberation of secretory granules (Odeblad,1973). The quantity of secretion liberated depends on:
a) The number of secretory units in the cervical canal.
b) The percentage of cellular mucus secretion per unit.
c) The response of the secretory cells to the circulating hormones.

In a normal woman of child-bearing age, there are about 400 secretory units of mucus in the cervical canal. The daily production of mucus varies from 600 mg at midcycle to 20-60 mg during other periods (Odeblad, 1977).

The Biophysics of Cervical Mucus
At the beginning of his studies, Odeblad thought that all the crypts produced secretions at the same time.

In 1966, Odeblad discovered that some of these crypts were responsible for the fine mucus secreted on days close to ovulation and produced crystals when the mucus was air dried on a slide. Other crypts producing thick mucus did not crystallize and were obtained in the infertile phases of the cycle.

The first type of mucus discovered by Odeblad in 19668 was named E (estrogenic) and the second, G (gestagenic).

In 1977, Odeblad proved that Type E had 2 components:
1. S (sperm conveying)
2. L (locking in low-quality spermatozoa).

He observed that Type S mucus crystallised into thin, parallel, needle-like structures, yet Type L showed a
fern-like morphology, with crystals forming a central axis from which long branches fanned out at an angle
of 90º.

In 1977 Dr. Kevin Hume learned that Professor Odeblad was to make a visit to Sydney, Australia, in response to an invitation coming from a group of veterinary scientists.

Dr. Hume was able to attend Professor Odeblad’s presentation and afterwards informed him of the development of the Ovulation Method, providing him with copies of the Ovulation Method teaching materials which he took away for further study.

About two years later he reported that he had gone back over the records of his own research into the activity of the cervix of the uterus during the ovarian cycle, in his capacity as Professor of Medical Bio-Physics in the University of Umeå. He said that he had been surprised and delighted to find that the work that had been carried out in Melbourne precisely coincided with his own studies in Umeå and that the guidelines that had been devised in Melbourne for the use of the Ovulation Method were certainly correct. Professor James
Brown added that the Ovulation Method has a rule to provide for every situation the woman may encounter during the reproductive era of her life.

“In 1983 I had the privilege of working with Drs. John and Evelyn Billings in Melbourne and also with Professor James Brown and other research workers of the Ovulation Method”, Odeblad said.

“The hormonal response of G, L, and S mucus was studied. We found that L mucus was stimulated by medium and increasing levels, and S mucus by high levels, of oestrogen. Later I showed that S mucus was also stimulated by noradrenaline. G mucus was stimulated by progesterone. In the first infertile phase of the
cycle the progesterone level is low, but sufficient to stimulate G crypts feebly (G- mucus). After ovulation, progesterone levels are high and stimulate G crypts strongly. This G mucus is very dense (G+ mucus)” (Odeblad).

In 1992 Odeblad described an additional type of mucus, present in lesser quantity, called P (peak), as it has its maximum secretion on the Peak (ovulation) day.

Several studies indicate that P6 mucus most probably is responsible for the peak sensation of slipperiness (2011).

On the other hand, we have to consider Odeblad´s studies with Nuclear Magnetic Resonance (NMR). These studies started in 1953, when he was awarded the Rockefeller Foundation Fellow at the University of California, Berkeley and Standford.

He was the first researcher to bring NMR to Europe through Sweden.

In 2003, Paul C. Lauterbur received the Nobel Prize in Physiology of Medicine. In his Nobel lecture, he said:c“Actual medical measurements were started when Erik Odeblad, a Swedish M. D., constructed apparatus and devised methods to study very small quantities of human secretions for medical purposes”.

Also in 2003 I had the privilege of publishing a paper with Prof. Odeblad in Human Reproduction12. It was also coverfront and Prof.Odeblad was delighted by that. It referred to the work of my doctoral thesis, which was done with his priceless help.

On 25 May 2012, Prof. Erik Odeblad received the European Magnetic Resonance Award 2012 in a special
ceremony in Umea, Sweden.