Cervical mucus


While some think of it as regular vaginal discharge, others understand that cervical mucus can be a practical indicator of female fertility. Especially when planning for a baby, it makes sense to take a closer look at the cervical mucus as it reveals when we are in our most fertile phase and chances for a baby are at an optimum!

What exactly is cervical mucus?

The cervix is the neck-like opening to the uterus, which opens and closes cyclically. In the overlying glands, cervical mucus of varying quality is produced, which gives information about whether we are in our fertile phase or not. Sometimes the cervical mucus is thick and impermeable and thus closes the cervix to protect us from germs. It also works to prevent sperm from entering, as the body is hormonally not yet ready for the ovum to get fertilized. On the other hand, when our body is ready for conception, the cervical mucus is more fluid and even sugary in order to protect, filter, nourish, and direct sperm.

How is the cervical mucus checked?

Understandably, this is not everybody’s ‘thing,’ but it's not nearly as uncomfortable as you may think. You do not necessarily have to put your fingers all the way up into your vaginal canal. The mucus located directly at the vaginal opening is sufficient to check its consistency. You simply take some mucus with the index finger (possibly together with the middle finger) and check, as shown in the graphs, if the mucus is rather creamy, watery or stretchy. You may have noticed that, in your most fertile phase, the toilet paper "slips" or more mucus residue remains after wiping - you can evaluate this mucus just the same way as described above.

How does cervical mucus change during the cycle?

Our graph shows the relationship between fertility, basal body temperature, hormones and the consistency of cervical mucus before ovulation (see blue bordered graphic).

How does the cervical mucus change?

Infertile: dry and impermeable

Glands at the base of the cervix usually produce this type of mucus after menstruation and after ovulation has taken place. Once menstrual bleeding stops, the cervix closes and a mucus that is impenetrable for sperm is blocking the way into the uterus. This type of mucus is usually not visible at the vaginal opening, hence there is little or no visible discharge, and the vagina feels somewhat dry. How long this phase lasts at the beginning of the cycle depends on the degree of ripeness of the regrowing follicles and whether their growth is affected by external influences, such as stress, a strict diet, extreme sports, etc., all of which can cause a delay in the process. While this phase may be skipped completely in very short cycles, wet and dry phases can alternate several times in very long cycles. Male sperm cannot withstand this acidic vaginal environment and thus survival is a maximum of 3 hours.

Infertile: Dry

Possibly fertile: sticky, lumpy to creamy

More and more oestrogen is produced inside the growing follicles and the hormone is passed through the bloodstream to, amongst other places, the brain and the cervix. Now the glands located a little higher up in the cervix produce sticky lumpy mucus that gradually becomes more fluid and creamy. The vagina becomes more moist and now you can see more traces of the cervical mucus at the vaginal opening. These are the first signs that you are entering your fertile phase. It is still difficult for the sperm to move rapidly, but they can now protect themselves from the acidic vaginal environment, even if only for a short time, thanks to the consistency of the mucus.

Possibly fertile: Sticky and creamy phase

Fertile: Liquid and elastic

A few days before the follicle is ready to rupture and release a matured egg into the fallopian tube, the estrogen level rises sharply. The vaginal climate becomes moist, and the mucus is now produced in the glands in the upper area of the uterine canal. This estrogen mucus is stretchy and fluid, often even ‘spinnable,’ very similar to raw egg white or even more watery. This mucus protects, filters, nourishes and transports the sperm, and the sugar contained in it, luring them into the cervix. The sperm can survive here for 3 to a maximum of 5 days. This is now the best time to be intimate if you are planning for a baby. To make sure enough live sperm, which can ascend toward the fertilizable egg, is present at any time, it is recommended to be intimate every 2 days during this time.

High fertile: Clear phase

After ovulation

A gland that produces progesterone develops from the remaining follicle that ruptured and released the egg. This hormone then circulates throughout the body via the bloodstream. Basal body temperature increases measurably and the mucus, now being produced by the glands in the lower section of the cervix, becomes impermeable again, closing the cervix.

Differences in the cervical mucus pattern

It is important to note that various factors can influence mucus quality, which can somewhat complicate its evaluation. Stress as well as sexual arousal can cause a temporary increase in vaginal discharge, whereby the latter can even appear to be spinnable mucus as seen before ovulation, when really, it is not1. Furthermore, cough medicine amongst others can liquify the discharge, which should also not be confused with the mucus quality typical for ovulation or impending ovulation2. Therefore, it is only in combination with a rise in basal body temperature that it can be safely assumed that the mucus quality was actually caused by rising oestrogen levels, marking the beginning of the fertile phase3.

In various forums, women share their experiences as to how cold remedies and asthma sprays were found to have had an influence on their cervical mucus quality due to their decongestant effects. Unfortunately, no clinical study has been conducted to this day that supports or invalidates those claims.

Improving cervical mucus quality

It is possible to improve the quality of the cervical mucus. This is relevant for you if you do not see or feel any type of change in your vaginal discharge during your fertile phase. Especially when planning a baby, this can be of utmost importance. Vaginal discharge consists mostly of water, so it is very important that you make sure to drink enough so that the mucus can become increasingly fluid and easier to interpret. To achieve this, it is best to drink herbal teas and, of course, water. Caffeine or alcoholic beverages have the opposite effect. They dehydrate the body and make the cervical mucus more viscous. One study concluded that consuming more coffee (several cups a day) may, among other things, make conception take twice as long4.

Why does Daysy not use cervical mucus data for evaluation?

You have the opportunity to take note of the nature of your cervical mucus for your own personal use via Daysy’s app DaysyView, however, there is no standardized, reliable method to objectively observe and assess mucus quality - especially in view of the various factors that can affect the nature of the mucus for each individual. We want Daysy to be easily usable by any woman without requiring a thorough understanding of cervical mucus or the fine details of cycle analysis. We want Daysy to be straightforward and reliably applicable for all women, while minimizing the possibility for misinterpreted cervical mucus evaluation.

The Daysy algorithm combines attested cycle knowledge with the evaluation of individual characteristics. Based on the daily measurement of the basal body temperature as well as the entries of menstrual data, the individual fertile days are determined through the use of statistical methods.


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1) Nansel, T. R. et al. The association of psychosocial stress and bacterial vaginosis in a longitudinal cohort. Am. J. Obstet. Gynecol. 194, 381–6 (2006).

2) Check, J. H., Adelson, H. G. & Wu, C.-H. Improvement of cervical factor with guaifenesin. Fertil. Steril. 37, 707–708 (1982).

3) Gnoth, C. et al. Optimizing natural fertility: a committee opinion. Fertil. Steril. 100, 631–637 (2013).

4) Hassan, M. A. . & Killick, S. R. Negative lifestyle is associated with a significant reduction in fecundity. Fertil. Steril. 81, 384–392 (2004).

Authors: Niels van de Roemer, Andrea de Groot, Petra Schenke