Tracking your fertility with cervical mucus

Cervical mucus is a vaginal secretion produced by the cervix under the influence of oestrogens. These are the hormones that guide the beginning of the cycle, the luteal phase.

It actually takes its name from where it is produced, as "cervix" means neck of the womb in Latin.

Cervical mucus production

Concretely, with each new menstrual cycle (that is, from the first day of each period), a hormonal dialogue is established between the brain and the ovaries. This allows a follicle to grow until it reaches a size sufficient for ovulation. The brain signals to the ovaries to prepare a stock of follicles, which begin to develop and produce oestrogens. As the cycle progresses, the follicles grow larger and these hormone levels rise.

Cervical mucus is produced in response to this rise in hormones. It is often confused with vaginal discharge. Vaginal discharge includes cervical mucus but also other vaginal secretions and dead cells. Vaginal discharge has a more general role in cleansing and protecting the vagina.  

The importance of cervical mucus

The role of this mucus is to allow sperm to reach the egg that is about to be released. When it is not present (roughly ¾ of the cycle), the vagina is so acidic that sperm survive only a few seconds. Fertilisation is impossible. Cervical mucus has a pH that allows sperm to remain viable for up to 5 days in the crypts of the cervix!

It also plays a protective and supportive role for sperm in the vagina. It retains sperm within its tightly woven mesh and guides them upwards towards the egg.

This is why you are fertile for around 6 days per menstrual cycle: 5 days before ovulation, thanks to the cervical mucus, and 1 day after, as the egg survives for 12 to 24 hours. Outside this window, pregnancy is not possible.

In the event of pregnancy, the cervical mucus forms the mucus plug. This plug helps to protect the embryo. 

It has been extensively studied as a fertility indicator for women trying to conceive.

First of all, there is not just one type of cervical mucus — there are several, each more or less fertile. Its appearance, texture, and quantity change throughout each phase of the cycle. It can be assessed in two ways: firstly, by its consistency, which you can observe in your underwear; and secondly, by the sensation it produces — the feeling of moisture it brings.

Cervical mucus during and after your period

During the infertile phases of the menstrual cycle (during the follicular phase — that is, during and after your period, although in a short cycle you may enter your fertile window as soon as your period ends — and then between ovulation and the next period): no mucus is observed, or only a non-fertile, crumbling mucus known as G-type mucus, which serves to block the cervix. By the end of the day, your underwear is either dry or dotted with sticky discharge. The texture is pasty and thick, leaving a crust but with no sensation of moisture. The overall feeling is therefore dry during the follicular phase.

Cervical mucus at the start of the fertile window

As you enter the fertile window, moisture begins to appear, along with mucus that is at first quite lumpy and possibly yellowish in colour (reminiscent of hummus — known as L-type mucus), then creamier (like body lotion — known as S-type mucus). During this phase, you begin to notice a three-dimensional consistency in your underwear. It is no longer just a dry crust. The sensation becomes wetter, and secretions become more abundant. 

Cervical mucus approaching ovulation

As ovulation approaches, cervical mucus reaches its peak quality and becomes more abundant. Its consistency becomes very fluid and stretchy, with a transparent appearance — similar to raw egg white or even oil. This is known as P-type mucus. It produces a very slippery, lubricated sensation.

A varied and balanced diet is beneficial for cervical mucus. In particular, the omega-3 fatty acid DHA, proteins, B vitamins, and vitamin D will be beneficial. Some prenatal vitamins can help you meet your needs during this period. More specifically, our supplements omega-3 pregnancy and vitamin D pregnancy can help during this period.  

Cervical mucus after ovulation

As soon as ovulation has passed, a sudden change in appearance occurs. There is a clear shift from that moist sensation back to dryness. Vaginal secretions become lower in both quality and quantity.

This is generally a sign that ovulation has taken place. Cervical mucus after fertilisation becomes thicker and less permeable, in order to protect the uterus ahead of embryo implantation. 

Towards the end of the cycle, it becomes thicker, stickier, and less abundant again.

Cervical mucus and early pregnancy

Cervical mucus continues to change after fertilisation. Even during pregnancy, you will experience discharge. Due to hormonal fluctuations, abundant white discharge may be observed in the first few weeks. It will be white, creamy, transparent, or possibly very pale yellow, with no odour or discomfort.

In the first few days (days 6 to 12), you may also notice some bleeding following implantation. This spotting is a sign that your baby has implanted successfully — there is no need to panic. 

If you notice anything unusual (pain, odour, heavy or persistent bleeding, etc.), do not hesitate to speak to your healthcare team (midwife, gynaecologist, GP, etc.). 

In addition to observing cervical mucus after fertilisation, another important sign in the symptothermal method is taking the basal temperature — that is, the temperature upon waking.

The remnant of the egg transforms into the corpus luteum, which produces progesterone, a hormone with a hyperthermic effect. As soon as ovulation has occurred, basal body temperature therefore rises, by around 0.3 to 0.5 degrees.

It is the combination of this peak of fertile mucus followed by a clear drying up and the rise in temperature that leaves no room for doubt: the ovary has released an egg.

In summary: cervical mucus appears a few days before ovulation, its quality increases over approximately 5 days until it reaches a peak of wetness when the egg is released, accompanied by a rise in temperature.

The appearance of cervical mucus marks the opening of the fertile window, and its disappearance combined with a rise in temperature marks its close. As a precaution, three days after this rise in temperature are counted before considering oneself infertile, when using symptothermal method as contraception.

Observing cervical mucus after conception is a tool that is at once more practical, more reliable and less costly than an ovulation test.

It is more reliable because it is very common for an ovulation test to come back positive even when your body was simply trying to ovulate but did not quite manage to complete the process. This phenomenon is common in cases of polycystic ovary syndrome, for example, and the consequence is that you may miss the "right moment" by believing you have ovulated when in reality it was just a false start. With the combination of cervical mucus and temperature, even if the mucus may suggest ovulation is being prepared, the absence of a rise in temperature will prevent it from being confirmed.

Conversely, some women ovulate with an LH level (the hormone detected by ovulation tests) below the sensitivity threshold of the test, and therefore miss their ovulation entirely.

Moreover, in addition to helping identify the fertile window, symptothermal tracking can help identify an imbalance or even anovulation, and allow appropriate action to restore the cycle.

Observing cervical mucus combined with temperature tracking is a natural contraceptive method that is far more reliable than is sometimes suggested.

Recognised by the WHO, it has a theoretical reliability index equivalent to that of the pill (less than 1% risk of becoming pregnant) and a practical reliability index that is also very good (2% to 8% risk depending on the method and calculations), provided it is applied rigorously after proper training.

To find out more, have a look at our article on symptothermal method and contraception. Ask your healthcare professional (midwife, gynaecologist, doctor, etc.) for more information. 

Cervical mucus — far more than a random or even shameful vaginal secretion — is therefore a wonderful tool for connecting with yourself and identifying your fertile window. Observing cervical mucus after fertilisation is therefore very useful.

Learning to observe it is knowledge that all young girls should have, so that when the time comes, they are able to make an informed choice about contraception, and/or to approach a pregnancy journey with awareness and confidence.

Do not hesitate to consult your healthcare professional (gynaecologist, midwife, doctor) if needed.