# The Discovery of Different Types of Cervical Mucus and the Billings Ovulation Method
Odeblad, E., 1994. The discovery of different types of cervical mucus and the Billings Ovulation Method. Bulletin of the Natural Family Planning Council of Victoria. Available at": [LINK](https://www.factsaboutfertility.org/wp-content/uploads/2017/01/Odeblad_DiscoveryZofZCervicalZMucus_1994.pdf)
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 1 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 S mucus, 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.
- cervical mucus is produced by the cervix
- cervical mucus
- cervical mucus plays a key role in the female reproductive cycle
- 10% of women ovulate the day before peak day
- the cervix has 4 different types of crypts which produce the 4 types of cervical mucus
- Progesterone stimulates the production of G Mucus
- Oestrogen stimulates the production of E mucus
- vaginal fluids are reabsorbed by the vagina in the infertile phase, but less so in the fertile phase (hence the flow outside the vagina increases)
- there are many different types of cervical mucus
- the cervix also has F cells which produce F mucus
- G mucus forms an impenetrable plug
- cervical mucus contains different components
- peak day is the last day in which fertile quality cervical mucus is observed
- the last day that fertile quality cervical mucus is observed in the day that ovulation occurs in 80% of cycles
- egg white cervical mucus is the principal indication of fertile days
- 10% of women ovulate the day after peak day
## Extracted Text
### [[egg white cervical mucus is the principal indication of fertile days]]
> 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 ^88oro
### [[peak day is the last day in which fertile quality cervical mucus is observed]]
### [[the last day that fertile quality cervical mucus is observed in the day that ovulation occurs in 80% of cycles]]
> 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. ^m2hcb
### [[10% of women ovulate the day after peak day]]
### [[10% of women ovulate the day before peak day]]
> Ovulation occurs on the preceding day in about 10% of cycles and in about 10% of cycles on the day following the Peak. ^m8l61
### [[vaginal fluids are reabsorbed by the vagina in the infertile phase, but less so in the fertile phase (hence the flow outside the vagina increases)]]
> 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. ^5fsq3
> The isthmus is a part of the uterus, localized between the body and the cervix and with a length of only 5-7 mm. Its glands produce a fluid, secretion Z, which probably contains several enzymes.
### [[the cervix has 4 different types of crypts which produce the 4 types of cervical mucus]]
> The cervix has four different types of crypts, denoted G, L, S and P, which produce the four types of mucus: G, L, S and P mucus. ^y7ef9
### [[the cervix also has F cells which produce F mucus]]
> Also, between the openings to the crypts there are some cells, F cells, which are not differentiated. These cells produce F mucus which probably does not have any physiological function but the G, L, S and P types have their specific functions in the reproductive process and have importance for the symptoms of fertility and infertility. ^zdyx9
## What is Mucus?
### [[cervical mucus is produced by the cervix]]
### [[cervical mucus contains different components]]
> Cervical mucus is produced by the biosynthetic activity of the secretory cells of the cervix and contains three important components: (1) mucus molecules; (2) water, (3) chemical and biochemical compounds (sodium chloride, protein chains, enzymes, etc.). ^jmu1h
### [[there are many different types of cervical mucus]]
> Mucus molecules have two important properties: (a) they are able to join together to make polymers or an extended three- dimensional network (i.e. a gel); (b) since they are glycoproteins their properties can vary widely. Thus different types of mucus are produced, for example G, L, S, P and F mucus, which form different networks or gels. Also, other substances-- ions, protein chains, and enzymes--are able to modify the interaction of the mucus molecules and, as a consequence, their biophysical properties. ^eojy2
> The biosynthesis of mucus is a complicated process. The epithelial cells are stimulated by oestrogens (S-, L- or P-cells) or by progesterone (G-cells). The hormone is bound to a receptor in the cytoplasm, and is then transported to the cell nucleus. The receptor + hormone complex then activates certain parts of the genetic material (DNA) which is transcribed to another type of genetic material (RNA) which, in turn, carries the genetic message to the place in the cell where the amino acids are arranged in the correct sequence to form the protein core of the molecule. Carbohydrate molecules are then attached by enzymes onto the protein core. The instruction to the cell how this should be done is probably different in cells of type S, L, P and G by information laid down in cells already during their embryonic development (see below).
> The response of the cells to oestrogen or progesterone stimuli is comparatively slow (from one to several hours). The S and P cells also seem to have access to a much faster response mechanism, the stimulation by noradrenaline acting on a beta receptor localized in a cell membrane. This response occurs probably within a few minutes and may be responsible for the "instantaneous" discharge that some women experience on acute stress, e.g. in "stage fright" or a sudden emotional upset.
## Identification and Description of G, L and S Mucus
### [[Oestrogen stimulates the production of E mucus]]
### [[Progesterone stimulates the production of G Mucus]]
> two types of mucus, one with a high viscosity (G) the other with a low viscosity (E). E mucus was stimulated by oestrogens and G mucus by progesterone, G mucus being produced in G crypts, E mucus in E crypts. ^j07q-
### [[cervical mucus plays a key role in the female reproductive cycle]]
> Studies (Odeblad et al. 1984) showed that S mucus was very fluid (Figure 5) and that sperm cells moved along the canal very rapidly in S mucus, reaching the S crypts in 3-10 minutes. L mucus had a medium viscosity. Unit structures of L mucus attracted malformed sperm cells or those which moved slowly, and this "filtration" of sperm cells is efficacious (Odeblad 1985). ^0u-pl
### [[G mucus forms an impenetrable plug]]
> G mucus has a high viscosity and forms a sort of impenetrable plug (Odeblad et al. 1983). ^ndr3a
> If we take a macrosample of cervical mucus and allow it to spread out on a glass slide we are able to see with the aid of a microscope some interesting patterns (Figure 6). L mucus shows very fine crystals in the shape of rectangular leaves. In S mucus one sees crystals of another configuration–small, thin needles. G mucus does not exhibit any crystals, but epithelial cells, leucocytes and lymphocytes. The nuclei of these cells are very abundant (Figure 7). NMR studies indicate that the water of S mucus is associated with the mucus in such a way as to form a structure which facilitates the forward movement of sperm cells (Figure 8; Odeblad 1966a).
![[mucus types 1.png|500]]
![[mucus types 2.png|500]]
> Usually no sensation is associated with G mucus, and the days are dry during the infertile phases. When oestrogen levels increase L mucus begins to be produced, and wetness is felt, firstly with a sticky sensation. Later, when oestrogen levels are high, and S mucus is also produced, there is a slippery or lubricative sensation (Figure 15), and this sensation remains until the Peak day. On that day oestrogen levels are already decreasing but the noradrenaline-like activity of the sympathetic nervous system causes stimulation of the S mucus. Figure 15 shows the temporal relations of the different secretions. After the Peak day G mucus is accompanied by a return to a dry sensation due to the abundant secretion of progesterone by the corpus luteum.
### G- and G+ Mucus
> The two variants of G mucus are produced by: the same crypts, depending upon the levels of progesterone in the blood. My studies in Melbourne showed a positive correlation between the amount of progesterone and mucin content and also the number of cells in the mucus. G mucus, especially G+ mucus, probably contains antimicrobial globulins, probably the substance which occasioned the inactivation of mycoplasms in my microbiological investigations, whilst the mycoplasms were able to survive in L and S crypts which were inactive in the post- ovulatory phase.
> It is important to recognize that the cells of G mucus are of three types: (i) epithelial cells; (ii) leucocytes; (iii) lymphocytes. Their proportions are variable, usually about 50% epithelial cells, 25% leucocytes and 25% Iymphocytes, but larger variations are possible, depending upon different factors. Certain women always have many lymphocytes, others have many leucocytes. Interleukins may play a role for the presence of lymphocytes and leucocytes (Cannon and Dinarello 1985). Local or general. inflammations are able to influence the proportions
> The viscosities of G- and of G+ mucus are given in Figure 5 and Table 2. The two types are impermeable to sperm cells. In non-ovulatory cycles the G+ mucus is not produced. During pregnancy, G+ is more viscous and is called Gp
### Age, Pregnancy, the Pill and Microsurgery
> In young women around puberty S crypts are very numerous. Normally they are replaced by L crypts, and at premenopause the number of S crypts is considerably reduced. This transformation of L S crypts is a normal process. There is also a G L transformation. Also some columnar secretory cells on the portio are replaced by stratified epithelium which advances in a centripetal manner towards the cervical orifice. The L S and G L transformations are partially reversed by changes during pregnancy, but they are partially accelerated by the Pill. These circumstances may be simply stated by the expression: a pregnancy rejuvenates the cervix by 2-3 years, but for each year the Pill is taken, the cervix ages by an extra year.
> If a woman takes the Pill for 10-15 years and then ceases taking it in order to achieve pregnancy, she may encounter some difficulties. Studies indicate that the number of S crypts are very few and, as well, the cervical canal will be very narrow. In such cases I have attempted to imitate, by microsurgery, the rejuvenation which normally occurs during pregnancy, that is to allow S cells to "take over" the L crypts. Sometimes, in about 40% of cases, this microsurgery was not successful.
### P Mucus
> Examination of microsamples of crypts, the cells of which were not able to take over an L crypt, presented some new results. The crystals were not needle-shaped nor did they have rectangular branching. The branching was hexagonal (Figure 9) and the crystals were very thin. Re-exaniination of the slides obtained during complete cycles indicated that this mucus was usually present in maximum amount on the Peak day. The new mucus was called P (- peak) mucus.
### F Mucus
> A detailed analysis of about 600 charts, several kept over a period of 2-4 years (totally more than 12,000 cycles), showed that several young women normally charted a number of days with yellow stamps ("yellow days") in the infertile phases, despite the fact that their gynaecological examinations were perfectly normal. Most of these young women were virgins who had never experienced any genital infection. A careful study of their slides showed the existence of a mucus which resembled G- or G+ mucus, but leucocytes and lymphocytes were very rare. Precise aspiration of this mucus showed that it was produced not in the crypts but in the epithelium covering the endocervical wall between the openings to the crypts (Figure 1).
> The cells which cover the walls of the canal are probably more original or fundamental than the cells which differentiate in the crypts. This assumption is sustained by the observation that the younger the woman the more abundant is the quantity of mucus of this type. I have called this secretion F (- fundamental) mucus and the cells F cells.
> The description of the mature cervix and crypts, shown in Figures 1 and 12, is valid for the fertile years of the healthy woman. To understand the mature cervix it is important to study the development of the cervix during embryonic life, during infancy, adolescence and also its regression during and after the menopause.
### The Role of the Vagina
> Not only the cells of the cervix but also the cells of the vagina produce a mucus which is made up of membranous glycoproteins. In the vagina there are intermediate cells which are able to contribute to the presence of mucus on infertile days. A reason for the very frequent appearance of a flow outside the vagina during those days is a reduction of the reabsorption by the pockets of Shaw (Figures 1 and 14). The pockets are situated in the inferior part of the vagina and the contribution of vaginal mucus emanates from the superior part. In this case a gynaecological examination is quite normal and cytological examination shows more intermediate cells. Examination of a slide by microscope also shows quantities of F mucus in the cervical "spread out" specimens.
> Normally the reabsorption by the pockets of Shaw is reduced in the fertile phase because of the thickening of the preovulatory vaginal epithelium (Odeblad 1989). The capacity for reabsorption during adolescence may be retarded and dry days may be absent. If a young woman commences to take the Pill, maturation of the pockets is even more retarded. Forthcoming papers will give more detailed presentations of the role of the vagina for the Ovulation Method.
![[mucus type table 1.png]] ![[mucus type table 2.png]]
### Early Infertile Days
> After menstruation there are usually some days of dryness in the genital parts outside the vagina, and green stamps are used for the record. G mucus and minimal quantities of F mucus and of vaginal fluid are produced (Figure 15). They are viscous and do not flow rapidly in the vagina. Active reabsorption takes place in the pockets of Shaw and all factors contribute to a sensation of dryness. Sometimes, in the young woman, F mucus is very abundant and as the reabsorption processes have not yet developed a crumbly or sticky sensation of dryness is felt and yellow stamps are used. In the older woman a similar situation prevails, since reabsorption is diminished after the menopause. Not only F mucus but also vaginal contributions lead to the use of yellow stamps. The term "Basic Infertile Pattern" is used by Billings et al. (1989) for the situation during the first infertile phase before follicle maturation begins and in other situations with absent or delayed follicular growth. On p. 21 of that publication it is stated that the Basic Infertile Pattern may be either (i) dry days, indicated by green stamps, (ii) an unchanging continuous mucus pattern (yellow stamps), or (iii) a combined pattern (green stamps for dry days, yellow stamps for unchanging, continuous mucus days). In that same publication (Odeblad 1989) some considerations are given on the combined role of the vagina and the cervix for vaginal discharge. In a forthcoming paper these considerations will be extended in the light of the new discoveries of the P mucus, the mucolytic factor, the F mucus and B secretion
### The Days of Possible Fertility
> Increased oestrogen levels elicit a secretion of mucus in the L crypts. Reabsorption by the pockets of Shaw is reduced (Figure 14) and a moist, sticky sensation commences and white baby stamps are used on the chart. Often and especially with young women there is a secretion of P mucus which has a mucolytic activity (the granules) and the plug of G mucus is dislodged and expelled. After 1-3 days there is a change, the elevated oestrogen levels stimulate the S crypts and a wet and slippery sensation (Odeblad et al. 1986) is felt, depending on the presence of L and S mucus. This phase is usually longer in the young woman (Table 3) and also with a mature parous woman. The wet and slippery sensation is much shorter in women approaching the menopause and in women who have taken the Pill for several years.
> The last day of the slippery sensation is the Peak day, which coincides with the day of ovulation in 80% of cases, and the probability of conceiving is highest on that day. It is very important to know that the quantity of mucus is usually not at its
> maximum on the Peak day.
> The quantity and also the stretchiness are greater on the day preceding the Peak. An exception is the older woman. For her the fertile phase is very short, only one or two days, and in this case, the quantity and the stretchiness are maximal during the Peak day. In the young woman P mucus increases afresh about the time of ovulation and the mucolytic activity is augmented. There are two effects of this phenomenon: (i) the lubricative sensation is increased; (ii) if pregnancy is desired, there is lysis of the mucus above the S crypts and sperm cells move upwards to the uterine cavity. Sometimes this augmented lubricative sensation is present for 2 days in young women. After the Peak day there are 3 days of possible but decreasing fertility. Green baby stamps are used on the chart unless some traces of discharge are present when yellow baby stamps are used.
### Late Infertile Days
> The late infertile phase (Figure 15) commences on the fourth day after the Peak. G+ mucus is produced and forms an impenetrable barrier in the cervix. Usually the sensation is one of dryness and green stamps are used. Normally there is a preponderance of G+ mucus and much less F mucus in the cervix, and vaginal mucus secretion is minimal. There is active reabsorption by the pockets of Shaw and the situation is very similar to the first infertile phase. On rare occasions some sticky mucus or vaginal discharge may flow and a yellow stamp is applied to the chart. On the first day after the Peak it is usual to find on a slide mucus types G, L, S, P and F, and also secretion Z, especially in young women (Table 3).
### Anovulatory Cycles
> These cycles vary enormously. Often there is a regression of a follicle for a week and cervical secretion resembles the situation on the first infertile days. On the day after the follicle has reached its maximum size all types of mucus are visible on a microscope slide (Figures 6a and 6b). Sometimes the follicle persists for 2-3 weeks before regression commences and at other times the regression is very rapid 2-3 days before menstruation.
> Some months after birth a very small number of follicles begin to grow but they do not reach maturity. In these attempts, waxing and waning of oestrogen levels are evident and wet days are appreciated. Ultimately an oestrogen level is sufficient to lead to maturation and ovulation with a Peak day takes place. It is important that these events are explained by the teacher. I have had access to only a small number of cervical samples obtained during breast-feeding. However, it seems remarkable that there is an unexpectedly large amount of P mucus during the regress of an episode of follicle growth, not leading to maturation. This question has to be further investigated in the future.
### General Diseases
> Anaemias. Anaemias are usually accompanied by an increased amount of L and S mucus. After treatment, these symptoms cease. Asthma. This illness does not alter the secretions, but treatments in which adrenaline-like remedies are used elicits an increase in the lubricative sensation. Jaundice. Jaundice is accompanied by liver malfunction, including metabolism of steroid hormones. Irregularities in menstruation and mucus secretion are common.
### Specific Diseases
> Inflammation of the Cervix and Vagina. These diseases are accompanied by an increased discharge and alterations in the quality of the flow. Fertile and infertile phases are sometimes indistinguishable. After treatment this imprecision is improved
> The Pill. Complications arising from the use of the Pill are very frequent. Infertility after its use for 7-15 years is a very serious problem. S crypts are very sensitive to normal and cyclical stimulation by natural oestrogens and the Pill causes atrophy of these crypts. Fertility is impaired since the movement of sperm cells up the canal is reduced. Treatment is difficult. In some cases hormonal treatment is possible. In very intractable cases I have tried to reconstruct the S crypts microsurgically with acceptable results but the treatment is difficult and time-consuming. As already mentioned, a careful study of unsuccessful micro-operations led to the discovery of the P crypts and the P mucus.