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How Cervical Mucus Helps Predict Your Most Fertile Days

There are many ovulation predictor kits on the market, but there’s one inside every woman that’s absolutely free. Cyclical changes in the secretions produced by the cervix provide a simple, easy way for women to monitor their cycles–and their most fertile times. As opposed to the change in basal body temperature that occurs after ovulation, the change in cervical mucus (CM) occurs several days prior to ovulation, giving women the opportunity to time intercourse for conception.

The cervix is the neck of the uterus, leading to the vagina. It’s not a smooth pipe, but a passage filled with crevices. In these nooks and crannies, CM is produced and released. Hormonal changes over the course of a woman’s menstrual cycle affect the amount and the consistency of CM. In a way, CM is the gatekeeper of the reproductive system. Sperm released into the vagina have to swim through the cervix–and its CM–and past the uterus if they are to successfully fertilize the egg as it makes its passage down the fallopian tubes.

For most of the cycle, CM acts as a barrier to sperm. It protects the cervix chemically–with white blood cells fighting foreign bodies–and mechanically–acting as a plug and closing the cervical canal.

But during the fertile phase, the consistency and composition of CM changes. Instead of being a barrier, CM now aids and accelerates the sperms’ passage through the cervix. CM during the fertile phase also extends sperm longevity, allowing them to live for up to five days within the female body. The CM even acts as a quality control device, screening the sperm and catching any with irregular or curved swimming.

By observing CM to pinpoint the fertile phase, women can help increase their chances of conception. Changes in CM will indicate the days leading up to ovulation, and sexual intercourse during this time will ensure that sperm—nourished by fertile phase CM—will be present when the egg is released.

What to Look For

A woman can monitor her CM by feel or appearance. The sensation of CM in the vagina–dry, moist, or wet–is one clue to follow for detecting impending ovulation. The color (white, creamy, cloudy or clear) and consistency (sticky, or smooth and slippery) are others.

Women can see and feel CM when it moistens their underwear, or when they wipe themselves with toilet paper. Bearing down (such as with a bowel movement) or releasing the muscles following a Kegel exercise may release more mucus. Women can also conduct a “finger test.” To do this, a woman should first thoroughly wash her hands, then carefully insert a finger into the vagina. When the finger is removed, she can observe and note the color and consistency of the CM by stretching it out between two fingers. Because it may sometimes be difficult to distinguish between CM and semen, it’s best to test CM before intercourse, or wait for a while afterwards. Cervical mucus can also be altered by vaginal infections, medication, and birth control.

The chart below gives the information for de-coding CM to detect ovulation.

Phase Sensation CM Appearance
Pre-ovulatory Dry No visible mucus.
Fertile Moist or sticky White or cream colored, thick to slightly stretchy. Breaks easily when stretched. 
Highly Fertile Slippery, wet, lubricated  Increase in amount. Thin, watery, transparent, like egg white.
Post-ovulatory  Dry or sticky Sharp decrease in amount. Thick, opaque white or cream-colored.

Barbara J. B. Clark, a certified physician assistant at Knox Ob-Gyn in Galesburg, Illinois, describes the most fertile CM as “raw egg white.” This fertile CM is clear, and may stretch several inches before it breaks.

Some women may think that gazing at toilet paper or performing an internal test is not only a bit odd, but even distasteful. But it’s a feeling worth getting over. Clark believes that women who check their CM “feel like they’re doing something to help.” They’re using their bodies’ signals to predict ovulation and help themselves conceive.  Our fertility calculator can also help you predict when the time is right.

This article originally appeared in the Fall 2005 issue of Conceive Magazine.

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