What’s cervical mucus?

Knowledge about cervical mucus is absolutely vital to understanding one’s fertility. Mucus is not unique to the female reproductive system. It is also present in places such as our throats, eyes, noses, stomachs, and bladders. Mucus membranes line many internal organs. The general function of our body’s various forms of mucus is to protect, clean and lubricate[i].

The cervix is a fascinating part of the female body, to be sure. It is an organ that connects the uterus and vagina, and measures one inch in diameter and is one-and-one half inches long with a canal that runs through it[ii]. The canal is lined with crypts that produce mucus according to the levels of the two dominant female sex hormones: estrogen and progesterone. This mucus is high in water content. Therefore, dehydration is one possible cause of limited cervical mucus. Certain medications can also dry up some of this good, healthy mucus.

Perhaps the most significant component of mucus to aid in understanding a woman’s fertility is how it changes throughout a woman’s cycle. 20-60 mg of mucus/per day is produced in a normal woman of child-bearing age. This increases to 700 mg/per day during the days immediately preceding ovulation[iii]. That is over ten times more mucus! It is no surprise that a woman can count on noticing this dramatic change that indicates impending ovulation.

What’s really fascinating is how mucus changes form at different stages of the cycle to facilitate or prevent the conception of a child.

When a woman’s estrogen is high, her cervical mucus plays the role of guide and protector of the sperm. It is nutrient rich, and it contains swimming channels that allow for sperm penetration. Its alkalinity neutralizes the acidity of the vagina (sperm are alkaline). In addition, perhaps the most intriguing of all these factors is the mucus’ ability to “filter out” bacteria and “abnormal sperm forms”[iv]. That’s right: a sort of natural selection happens within the human body to ensure that only the healthiest sperm meets the egg.

cervical mucus info_2
This graphic shows the cervix and the crypts that produce the mucus. To the left, we can clearly see the type E mucus (mucus days) with the channels for sperm. On the right, the mucus on dry days is very different, and blocks the entry to sperm. Image from Hilgers, T.W., Daly, K.D., Prebil, A.M. et al. The Picture Dictionary of the CREIGHTON MODEL FertilityCareTM System, Pope Paul VI Institute Press, Omaha, Nebraska, 2001

When progesterone rises after ovulation, the mucus dries up significantly and the type of mucus produced is no longer conducive to sperm transport. Known as the post-ovulatory phase, the drying of cervical mucus is a dramatic change that informs a woman that her time of fertility has ended until the next cycle.

Cervical mucus continues to fascinate me to this day. A majority of women do not know the purpose (and importance) of cervical mucus, but I believe we can change that. Here’s how you can help. Share this post, tell a friend about fertility awareness, or contribute financially to Natural Womanhood so we can continue to get this important information out to women, couples, and medical professionals.


[i] Encyclopedia Brittanica Mucus Membrane. http://www.britannica.com/science/mucous-membrane

[ii] Hilgers, T. Reproductive Anatomy & Physiology, 53.

[iii] Hilgers, T. Reproductive Anatomy & Physiology, 54.

[iv] Hilgers, T. Reproductive Anatomy & Physiology, 58.


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