Cervical Discharge Through the Menstrual Cycle

Cervical discharge, or mucus, changes in quantity, colour, consistency and feel throughout the menstrual cycle.

Carrying out on-going, rigorous, daily monitoring of cervical mucus can be a means of determining when you are ovulating. It is a form of natural family planning, often performed in combination with daily measurements of basal body temperature (BBT), and is most frequently used to help those who are struggling to conceive determine when they are most fertile. Conversely, it can be used as an inexpensive, entirely natural form of contraception by couples who are actively trying to avoid falling pregnant. However, unintended pregnancy rates are relatively high when women rely solely on their cervical discharge to determine when it is ‘safe’ to have unprotected intercourse.

Typical mucus secretions throughout the menstrual cycle

  • During period: mucus secretions probably absent. If there are any, it is difficult to distinguish them from menstrual blood.
  • Phase 1: 3 – 4 days post-period. No noticeable secretions, dry sensation. A latent phase of the cycle.
  • Phase 2: Next 3 – 5 days. Mucus becoming cloudy and sticky. Damp sensation.
  • Phase 3: Next 3 – 4 days. Abundant, clear, slippery and stretchy mucus. Wet sensation. The end of this phase is when ovulation occurs. This is known as the ‘peak day’.
  • Phase 4: Days after the ‘peak’ day and preceding the next period. Secretions become thick and sticky, there may be some dry days. Postovulatory, ‘luteal phase’ of the cycle.

The length of each phase may vary and it can take several months for a female to start recognising her monthly pattern. Once she is able to distinguish the different phases of her mucus cycle, a female that wishes to become pregnant will be able to increase her probability of conception by timing intercourse around those days of optimal mucus (phase 3), which will coincide with her fertile window. Four days after the peak day marks the end of the fertile window for that cycle.

If conception occurs, the mucus may become thick, gummy and clear and the woman may experience mild implantation bleeding. This should only last for 24 – 48 hours. During early pregnancy, cervical discharge may be sticky, and white or yellow in colour.

What is mucus and why does it change during the menstrual cycle?

Mucus is a complex mix of water, lipids, cholesterols, carbohydrates, inorganic ions and proteins. Thought to be primarily protective in nature, mucus is also secreted by the cells by the respiratory system and the digestive system. Cervical mucus forms a natural barrier to protect the upper female genital tract from potential pathogens. It is also a source of antisperm-antibodies.

Immediately before ovulation, cervical mucus becomes clear and runny; this is conducive to penetration by male sperm. When the cervical mucus is thicker and sticky in consistency, it naturally blocks the passage of sperm through the cervix. During normal conception, sperm must pass through the cervix to reach the egg. If the sperm cannot navigate through the cervix, fertilisation is not possible. It is feasible that using drugs to manipulate the composition of the cervical mucus, i.e. making it inhospitable to sperm, could one day serve as a non-hormonal form of contraception.

The changes in cervical discharge are believed to be due to fluctuations in hormone levels; with the clear wet ovulatory secretions, known to coincide with high oestrogen levels. The effects of hormonal contraceptives on cervical mucus are not widely understood and thus, women who use them are unlikely to be able to track their cycles in the same way. Women with irregular cycles or those who are anovulatory, will likely struggle to identify a consistent mucus cycle. This includes women who have just started their periods or are approaching the menopause, those who have recently given birth, stopped taking hormonal contraceptives, or stopped breastfeeding and those with hormonal conditions, such as polycystic ovary syndrome. Women who suffer from persistent genitourinary infections are also unlikely to be able to track their cervical discharge accurately.

When to seek further help

As described above, cervical mucus can vary significantly in quantity and consistently throughout the menstrual cycle. However, there are times when additional advice should be sought:

  • If the mucus is green, yellow or grey in colour.
  • If it is accompanied by excessive itching, or  a burning sensation.
  • If it smells.
  • If you experience abnormal uterine bleeding.

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  • Bigelow, J. L. “Mucus Observations in the Fertile Window: a Better Predictor of Conception than Timing of Intercourse.” Human Reproduction, vol. 19, no. 4, 1 Apr. 2004, pp. 889–892., doi:10.1093/humrep/deh173.
  • Ecochard, Rene, et al. “Self-Identification of the Clinical Fertile Window and the Ovulation Period.” Fertility and Sterility, vol. 103, no. 5, May 2015, doi:10.1016/j.fertnstert.2015.01.031.
  • Han, Leo, et al. “Cervical Mucus and Contraception: What We Know and What We Don’t.” Contraception, vol. 96, no. 5, Nov. 2017, pp. 310–321., doi:10.1016/j.contraception.2017.07.168.
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