top of page

Cervical Mucus and its Role in Fertility

Updated: Nov 30, 2023

Not only is cervical mucus an indicator of fertility, it is essential to enable conception to occur. Cervical mucus nourishes the sperm, protects them from the natural acidity of the vagina and guides them towards the egg.

The oestrogen peak, which stimulates the production of fertile mucus, usually starts about 6 days before ovulation. In response to this oestrogen, specialised glands in the cervix produce different types of mucus. The cervical mucus produced at infertile times (ie. all times except ovulation) is called G-type mucus. It is produced low down in the cervix, close to the vagina. It is thick, pasty and impenetrable, and it blocks the sperm’s entrance to the vagina.

As oestrogen levels rise, the more liquid L-type mucus is produced slightly higher in the cervix. This causes the vagina to feel more wet and sticky. The function of the L-mucus is to filter out some of the abnormal or poor quality sperm before they reach the uterus.

As ovulation approaches, a stretchy, slippery type of mucus, known as S-mucus, is produced even higher up in the cervix. S-mucus looks like stretchy egg-white. Sperm can survive up to 5 days in this mucus, and its consistency helps the sperm on their journey to the fallopian tubes.

If you are noticing S-type mucus, you are probably only a couple of days away from ovulation, and it’s the ideal time to try and conceive.

Finally, as ovulation is imminent, the mucus loses its stretch as the cervix produces P-mucus from the very top of the cervical canal. P-mucus derives its name from its rich potassium content. It activates sperm as they pass through the cervix to the uterus, giving them a final push!

The easiest way to evaluate the quality of the cervical mucus is to collect some on the fingers and see how much elasticity there is as the fingers are drawn apart.

The importance of recognising the changes in the fertile mucus lies in the fact that it precedes ovulation and therefore allows a woman to identify her most fertile window. The last day of fertile mucus is the day of peak fertility – the day before or the day the egg is released. Although the egg is the largest single cell in the body, It is one of the shortest-lived, being fertilisable for only 6-12 hours. Sperm, on the other hand, can survive up to 5 days in the female reproductive tract, although they are most able to fertilise the egg in the first 48 hours of delivery to the vagina. By allowing the sperm to travel up the cervical canal to the fallopian tubes in the days before ovulation, it ensures that hundreds of eager sperm should be lying in wait. Some studies have indicated that the day of sexual intercourse which leads to the highest conception rate is, in fact, two days before ovulation.

There are some medications that have an adverse effect on the cervical mucus and may hinder conception:-

👉 Antihistamines dry up mucus membranes all over the body, so, if you regularly take these, you might find you don’t notice your cervical mucus.

👉 Antibiotics can promote an overgrowth of candida or thrush. If severe, this may mask any evidence of fertile mucus.

👉 Some women may experience impaired fertility after stopping the combined oral contraceptive pill, even after the return of regular periods. It appears that the mucus produced by the cervix in these women is largely G-type, even though ovulation may be occurring, so sperm cannot gain entry to the cervix. This may last for up to 30 months after coming off the pill.

👉 Clomid, a fertility drug which stimulates pituitary activity, is anti-oestrogenic and it inhibits the mucus/producing glands in the cervix.

👉 NSAIDs lower prostaglandin levels and can influence the menstrual cycle and cause the fertile mucus to become scanty.

👉 Antidepressants, including SSRIs, can also reduce the number of days that cervical mucus appears.

At the core of Chinese medicine is the concept of Yin and Yang. Yin is cooling and moistening, whilst Yang is warming and drying. In Chinese medicine, oestrogen is a Yin hormone and progesterone is a Yang hormone. As oestrogen levels in the menstrual cycle rise, fertile mucus is produced and fertility reaches its peak. Therefore fertility mucus is Yin. Having sufficient Yin is also important for egg quality and the thickness of the endometrium.

If your fertile mucus is scanty or does not appear, Chinese medicine can help by supplementing the Yin and increasing oestrogen levels.

To book an appointment, you can call Conceive Clinic on 07957 641946 or email us on

Cervical Mucus

81 views0 comments


bottom of page