Cervical mucus changes throughout the menstrual cycle. These changes are typical and can indicate a person has ovulated. If the mucus looks like egg white, a person may be at their most fertile.

Some people monitor changes in their cervical mucus to help them get pregnant or to avoid pregnancy.

Read on to learn more about cervical mucus, how it changes during the menstrual cycle, how to check it, and how people use it for family planning.

A woman in a bathroom looking down in front of a mirror.Share on Pinterest
Taras Grebinets/Getty Images

Cervical mucus is fluid that the cervix releases into the vagina. It has several functions, including keeping the vagina lubricated and preventing infection.

Healthy cervical mucus ranges from clear to white or yellowy-white in color. Hormonal shifts throughout the menstrual cycle influence the amount, texture, and appearance of cervical mucus.

There may be more cervical mucus on some days than on others, and the color may shift from cloudy to transparent. These changes are a typical part of the menstrual cycle.

Some people use changes in cervical mucus to track their fertility, either to avoid pregnancy or to increase their chances of becoming pregnant.

Fertile discharge is thin, clear or white, and slippery, much the same as an egg white. It typically occurs around the middle of the menstrual cycle and lasts for about 4 days. Its appearance signals that ovulation is approaching.

Ovulation is when the ovaries release an egg. If the egg becomes fertilized by sperm, it may implant inside the uterus, resulting in pregnancy.

As the body prepares for ovulation, an egg ripens inside a follicle in one of the ovaries. As the follicle grows, it produces estrogen. The estrogen softens and opens the cervix slightly, and changes the texture of cervical fluid, making it more abundant.

This fluid helps sperm to move up the cervix and keeps them healthy on the journey, increasing the likelihood of fertilization.

Everyone’s menstrual cycle is slightly different, but in general, the changes in cervical mucus during the menstrual cycle follow this pattern:

  • Menstruation: Menstruation, or a period, begins the menstrual cycle. People cannot see their cervical mucus during this time.
  • 3 to 4 days after: There may be little or no discharge on these days. Sticky, glue-like fluid may follow. This is a time of low fertility.
  • Before ovulation: At this point, the body starts to produce more cervical mucus. For 3 to 5 days, the mucus may become thinner and look cloudy, white, or yellow.
  • Before and during ovulation: Just before ovulation, cervical fluid can become very wet and viscous. A person may be able to stretch the fluid an inch or more between their fingers. This lasts around 4 days.
  • After ovulation: After ovulation, the body releases the hormone progesterone, which dries up cervical fluid. The discharge may diminish in quantity and become thicker or cloudier. A person may have some days without any discharge. This phase usually lasts 11 to 14 days.

People who ovulate earlier or later in their cycle may not follow this pattern. Similarly, a person who does not ovulate may notice no fertile discharge.

Potential causes of a lack of ovulation include:

  • polycystic ovary syndrome
  • primary ovarian insufficiency
  • early menopause
  • underweight

This varies from person to person depending on the length of their menstrual cycle and when they usually ovulate.

Most ovulation occurs 14 days before a period. An egg only lives 12 to 24 hours after ovulation, but sperm can live up to 5 days in fertile cervical fluid.

This means that, for people wishing to become pregnant, the best time to have intercourse is 5 days before ovulation, and up to 1 day after.

Doctors call this the “fertile window“. Fertile discharge is one of the more reliable signs that a person is in their fertile window.

To determine fertility, check the appearance of cervical fluid at least once a day, beginning on the first day after a period.

Planned Parenthood suggests three ways people can do this:

  1. Wipe the opening of the vagina with white toilet paper before urinating. Check the color and consistency of any fluid on the tissue.
  2. Look at the discharge that may be present on the underwear.
  3. Wash the hands and gently insert a finger into the vagina. Remove the finger and note the color, texture, and general appearance of the fluid.

Whichever method people use, they should record the results on a chart, in a diary, or using an app.

If they plan to use the information for family planning, they must do this for several cycles, so they can get a sense of what is typical for them.

Some people use cervical mucus tracking to avoid pregnancy. This is known as the cervical mucus method (CMM), and it is a form of fertility awareness method or natural family planning.

The CMM relies on a person having a consistent menstrual cycle and accurate knowledge of their cervical mucus so that they know which days are “safe” or “unsafe” to have penis-in-vagina sex without using birth control.

In theory, the “unsafe” days include:

  • during menstruation, especially if a person has a short cycle
  • a few days after menstruation and before fertile discharge begins
  • the fertile window

The “safe” days are:

  • after ovulation, when the fertile discharge has stopped, which usually lasts around 11 to 14 days
  • for some people, a few days into their period, if they have a long menstrual cycle

When beginning the CMM, people should not have sex without birth control for at least the first complete menstrual cycle. Tracking their cervical mucus for several cycles will give them more of an understanding of when their “safe” or “unsafe” days are.

However, it is important to understand that even with this knowledge, cervical fluid and the menstrual cycle can change.

Cervical mucus is not always a reliable indication of when a person is or is not fertile. Some things can make cervical fluid appear more slippery and elastic than it is, including:

Some people also naturally produce less fertile discharge than others, bleed between periods, or may have irregular periods, which could cause them to ovulate at unpredictable times.

If these factors influence a person’s cervical mucus, the CMM may not be a suitable method of family planning for them, especially if they want to be certain they will not become pregnant. The CMM also does not protect against STIs.

Similarly, a person trying to conceive may want to track ovulation using other methods, such as ovulation tests.

People should contact a doctor if they notice any unusual changes in their cervical mucus, such as:

  • much more discharge than usual that does not go away
  • a strong, unpleasant odor
  • discharge that is watery and gray
  • discharge with a white, cottage cheese-like texture
  • discharge that is yellow or green

These can be signs of infection.

People can also contact a doctor if they suspect they are not ovulating or are having difficulty conceiving.

Cervical mucus changes over the menstrual cycle, and as such, it can indicate when a person is fertile or about to ovulate.

Because of this, some people use these changes to predict when they might be most likely to get pregnant. For some, this helps with conceiving, while for others, it can be a way to avoid pregnancy.

However, many factors influence when and how cervical mucus changes throughout the cycle. Each person’s rhythm is different, and activities such as sex or changes in health status can influence cervical fluid.

Anyone who has questions about this family planning method or notices unusual changes in their cervical mucus should speak with a doctor.