SCIENTIFIC VERIFICATION OF THE OVULATION METHOD BY DR. ERIK ODEBLADErik Odeblad, M.D.,
Professor and Chairman of the
Department of Medical Biophysics,
University of Umea, Sweden, and
former research fellow of the Swedish
Medical Research Council, Department
of Obstetrics and Gynecology,
Karolinska Institute, Sabbatsberg
Hospital, Stockholm, Sweden.
Cervical mucus is a complex secretion produced constantly by the mucus secreting epithelial cells of the endocervix. There are approximately 400 mucus-secreting glandular-like units (crypts) in the cervical canal which produce mucus at the rate of 20 to 60 mg per day in normal women of reproductive age. During midcycle, the amount increases tenfold and may reach up to 700 mg per day.
The most important constituent of cervical mucus is a hydrogel, rich in carbohydrates and consisting of glycoproteins of the mucin type. (A glycoprotein is one of a group of protein-carbohydrate compounds among which are the mucins; a mucin is a proteinaceous material which when combined with water forms mucus.) Most of the physical properties of cervical mucus are due to mucins.
Cyclic alterations in the consistency of cervical mucus influence sperm penetrability, nutrition, and survival. Optimal changes of cervical mucus properties, such as greatest increase in quantity, spinnbarkeit, ferning and pH, and decrease in viscosity and cell content, occur immediately prior to ovulation, and are reversed after ovulation. Pre-ovulatory mucus is most receptive to sperm penetration.
The secretion of cervical mucus is regulated by the ovarian hormones. The components of the cervical mucus change markedly during the cycle, reflecting the preponderance of estrogens or progesterone. The secretion of different types of mucus and, accordingly, their biophysical properties (i.e., spinnbarkeit, crystallization, and consistency) are largely determined by these hormonal factors.
The structure and function of the mucus and its relation to fertility and infertility have been most thoroughly investigated by Dr. Erik Odeblad and his colleagues at the University of Umea in Sweden. The following are some of their findings:
1. The key to nearly all the present research was the discovery, first published in 1976, that there are three types of cervical mucus, G, L and S.
G mucus seals the cervical canal during the infertile days of the cycle. It is present in one variety immediately after menstruation, in another during the post-ovulatory phase of the cycle, and probably in a third during pregnancy.
The post-menstrual G mucus is supplanted by L mucus when the circulating estrogens rise. The L mucus, the first mucus symptom of the cycle is a soft, mucinous secretion which turns into a slippery, watery secretion a few days before ovulation when S mucus is produced. The S mucus, the sperm receptive mucus, provides low viscosity channels for the sperm by which they gain access into the cervix and uterine cavity. A certain balance between the S and L secretion seems to be necessary for optimum fertility. Shortly after ovulation, both L and S mucus disappear and the post-ovulatory G mucus appears.
When performing the spinnbarkeit test, one can see that the mucus thread is uneven due to the presence of different types of cervical secretion. The S and L types are transparent, the G type is opalescent. The thin parts of the thread denote the S mucus.
2. The ovulatory mucus is a mosaic made up of mucus strings and mucus loaves. The strings contain the fluid gel, S mucus, and the loaves the more viscid gel, L mucus. The S mucus is very thin and flows rapidly between the loaves of L mucus. The strings are about 100 um in diameter and 2-3 cm long. The loaves are ellipsoid and 0.3x1x3 mm in size. Near the external os, there are some units of still more viscid G mucus.
The S secretion composes approximately 30 percent of midcycle mucus and the L secretion 70 percent, although there is a day-to-day percentage variation due to the continuous secretion and outflow of the mucus.
3. The ellipsoid units of L mucus provide the mechanical framework for the fluid S mucus and act as a trapping mechanism for sperm which are presumably not suitable for fertilization.
4. S and L mucus are produced by different secreting areas of the endocervix. The upper part of the cervix tends to secrete most of the S mucus. The peak symptom of the mucus.
This picture indicates a string of S mucus, the flow of secretion being indicated by arrows. This flow orients the mucin molecules. Then they interact and form micelles. One sperm is indicated to swim upwards. Another sperm, morphologically defective by angulation, is liable to deviate towards the borderline of the S string, and finally it enters the L mucus and becomes captured.
5. The time around ovulation when the S mucus is produced seems to be age dependent. In young women the S mucus is normally present for a longer time. At the age of about 20 years, the average time for S mucus secretion is about 4-5 days, while at 35 years, the average time is only about 1-2 days. A statistically significant correlation up to the age of about 35 years has been found. Also the spinnbarkeit changes with age in a similar but more complicated way.
6. Studies on the dose-response curve for the L and S mucus on estrogenic stimulation indicate that the L mucus requires only low doses of estrogen in circulating blood, while the S mucus requires higher levels. This finding easily explains why L mucus occurs before the S mucus in the normal cycle. But it is still not understood why the S mucus can be produced when the estrogen levels decrease after the estrogen peak. This is presently being studied in detail.
7. The flow of S mucus orients the mucin molecules, which then tend to form long thin aggregates, called micelles, separated by a waterlike medium, which permit very rapid sperm advance.
8. The anatomy of the mucus mosaic is such that some sperm swim to the uterine cavity, but most move to the S secreting crypts in which they seem to hibernate and form a sperm reservoir with a half-time of about 15 hours.
9. The advance of high-quality sperm seems to be a highly ordered process, in formal agreement with mathematical group theory. This indicates that some kind of intercommunication between the sperm cells exists, phonons being the carriers of intercellular messages.
10. A simple method has recently been developed to study the length of the micelles formed when the mucin molecules in S mucus line up in the mucus flow and aggregate forming these molecular chains of various lengths. The preliminary studies have shown that when the secretion of S mucus begins, the micelles are short, a minute fraction of a millimeter. After several days the micelles are longer and on the day of ovulation have an average length of about one millimeter; after ovulation they continue to aggregate, and also form branched structures. In cases of infertility of cervical origin, for example after the Pill, the micelles do not have the capacity to grow, but remain short, a situation that apparently is unfavorable for sperm progress in S mucus. This quality factor of the S mucus is extremely important and requires extended studies.
11. Post-IUD inflammatory conditions and other similar sequelae of sexually transmitted diseases, many of which have been promoted by the use of the Pill, are also being studied. It seems that inflammatory conditions may influence the capacity of the cervix to produce mucus of good quality. In depth studies in this particular field have not yet been conducted.
The cyclic variation of percentage of G, L, and S mucus based on 1,124 cervical samples. Immediately after menstruation the G type dominates. When the estrogen stimulus on the cervical mucosa increases, the mucosa responds with increased L secretion. The S mucus does not increase until 1-2 days before ovulation and is actually high also the day after ovulation when it then decreases suddenly. The L mucus decreases about one day before the S mucus. During the corpus luteum phase, the G mucus dominates. The day after ovulation, the G mucus is secreted from crypts in the lowest part of the cervix and the external os. This aids to close the cervical canal at its lower end. Above this "closed door" there is a very loose or liquid mucus "plug" consisting mainly of S mucus and containing the sperm released from the crypts which have been colonized during the first phase of sperm advance. The whole upper part of the cervical canal now acts as a big sperm reservoir, capable of continuously exposing the ovum to sperm.
1. "The Biophysical Properties of the Cervical-Vaginal Secretions," Erik Odeblad, Human Life Center, Collegeville, Minnesota, 1983.