Cervical fluid 101

Let's talk all about your #1 sign of fertility - that magical substance called cervical fluid, cervical mucus, or the "clear flow!”

In this post I'll explain:

• What cervical fluid is

• How to distinguish cervical fluid from other types of secretions you'll see throughout your cycle

• The different types of cervical fluid

• Normal secretions vs abnormal discharge
  

DISCLAIMER

This blog post is NOT enough information for you to start using FAM, and it's not meant to give you absolutely everything you need to know about cervical fluid. Your body is unique, and no source can ever possibly explain the different variations in what you may see coming from your own body. I encourage you to start doing your own research after reading this post and start tracking what you see!

WHAT IS FERTILITY AWARENESS/THE FERTILITY AWARENESS METHOD?

Cervical fluid is THE KEY to the practice known as Fertility Awareness or FAM. It involves observing and charting your daily signs of fertility or infertility: cervical fluid (also called cervical mucus), basal body temperature (your temperature when you first wake up), and optionally, cervix changes (height, texture, openness, position). Charting these signs each day takes about 1-2 minutes and can be used for natural birth control, conception planning, cycle understanding, and becoming the expert of your own reproductive health (if that sounds epic, IT IS - imagine having more intel about your own body than a doctor, app, or test!). You can learn all about how FAM works and what's involved with my free intro course!

TERMINOLOGY

Period = menstruation

Cycle = the time from one period to the next

Ovulation = the act of releasing an egg

Fertile window = opened by the first appearance of cervical fluid OR a calculation rule, and closed by the last appearance of cervical fluid and a shift in basal body temperature.

WHAT IS CERVICAL FLUID? (CF)

Before we jump in...You may have searched terms like "fertile discharge" or "ovulation discharge" trying to find out more about this mysterious cervical fluid stuff. Let's banish the word "discharge" right here and now; that's a term I prefer to save for actual infections and bacterial overgrowth. More on that later on in this post!

Cervical fluid is a special type of secretion that's made inside the cervix - the bottom part of the uterus that meets the vagina - ONLY in the days leading up to ovulation (plus the day of, and sometimes a couple days afterwards). It is the only way that sperm can get out of the acidic vagina and into safety while they wait for ovulation to occur. Hence, many of us owe our entire existence to cervical fluid!

Without cervical fluid, sperm can only survive about 4 hours.

However, WITH cervical fluid, they can survive up to 5 days.

Add in the 24 hours max that an egg can survive after ovulation - plus another 24 hours if a second egg is released - and you get a 7-day window of fertility each cycle where pregnancy is possible.

BUT! Since we cannot know in advance when that 7-day window will occur - AND because you will most likely see more than 5 days of cervical fluid in your fertile window - your fertile window will probably end up being more like 10-13 days. If you have long cycles (35+ days) you may see a few different fertile "patches" of cervical fluid that don't result in ovulation (though ovulation may eventually occur).

With FAM we use very specific rules and protocols to determine when the fertile window opens and closes. This means there's no guesswork or predicting required, since we assess fertility status on a daily basis.

On the left you can see how hard it is for sperm to try to swim without cervical fluid. On the left, sperm are easily able to swim in cervical fluid. Image courtesy of Kegg.tech

HOW IS CF MADE?

CF is specifically made in your follicular phase, or the phase leading up to ovulation.

Your cycle can actually be broken up into two distinct phases:

Follicular: from day 1 of your period to ovulation

Luteal: from ovulation until the day before your next period

The follicular phase (named after the follicle that holds the egg) is when about 1 dozen follicles begin to mature in the ovaries. The follicle is like the sac that holds the egg, and it undergoes the most change leading up to ovulation (the egg doesn't go through many changes at all until right before ovulation!).

Eventually, one follicle emerges as the dominant one (the other follicles just fade way right there in the ovary). About 10% of the time, 2 follicles will reach maturity, resulting in 2 eggs released at ovulation, but always within 24 hours of each other.

Now, most of the time you are actually not fertile, so the cervix is covered by a thick mucus plug that prevents any visitors (sperm, pathogens, bacteria) from entering the sacred gates.

But, under the influence of estrogen, the cervix releases this protective covering and begins to make cervical fluid!

The follicle is what makes this estrogen, which activates the cervical crypts - hundreds of tiny channels inside the cervix. And voila - you start to see cervical fluid!

As ovulation gets closer, cervical fluid becomes more wet and abundant, leading to what we call Peak Day: the last day that you see any quantity of your wettest type of CF.

Once ovulation happens, you transition into the luteal phase.

The luteal phase is named after the hormone gland that the follicle transforms into after ovulation: the corpus luteum, which is Latin for yellow body.

The follicular phase is variable in length - meaning, it takes a different amount of time each cycle for you to reach ovulation, so this phase might be 10 days one cycle and 17 days the next (I would say a healthy range for the follicular phase is 10 - 20 days, though this may be much different if you're in your teens; if you're perimenopausal; if you're postpartum; if you're recently off hormonal birth control; and if you have long cycles).

But the luteal phase is a FIXED 12-16 days (unless you have low progesterone, in which you might see less than 12 days, though specifically I would say 10 days or less). This means that after you ovulate, you will have about 2 weeks before your next period comes. With FAM, you can identify the first day of your luteal phase by the first day of your temp shift (or the first day after Peak Day, depending on what method you're using...yep, there are many different FAM methods!).

With the luteal phase, things totally shift: whereas you were estrogen-dominant before, with all that juicy cervical fluid and fertility, the luteal phase shuts off the possibility to ovulate again by producing progesterone, which sends a negative feedback signal to the brain for NO MORE OVULATIONS, NO MORE FERTILITY THIS CYCLE, thank you very much.

I repeat: after you have ovulated, you can't ovulate again for the entire rest of your cycle. Ovulation is a big hormonal event that takes a lot of synchronicity and effort between the entire endocrine system, and although you can release 2 eggs during ovulation, you cannot ovulate twice in one cycle.

I don't care what you've read on the news about twins being different ages or whatever (that's a blog post for another time). You cannot ovulate twice in one cycle. I HAVE SPOKEN.

Anyways!

Progesterone dries up cervical fluid, but that doesn't mean you will be completely bone dry the rest of your cycle and that you won't still see some type of secretions. The vagina is a mucus membrane, so you will always see some kind of moisture, like if you touch a finger to the inside of your cheek. See how there's just a sheen there? Or, you might see something different than that in your luteal phase.

Let's move on to talking about the different types of secretions you'll see throughout your cycle.

Another visual of how your hormones and fertility signs work throughout your cycle. (Please do not use this image without crediting me.)

TYPES OF CERVICAL FLUID

Now, be aware that there are MANY different FAM methods, and they each explain CF and other secretions a little bit differently. This is the classification system that I teach, and it's honestly not that different from terminology you'll find from most FAM methods. Same language, different dialect!

The 5 States of Secretions:

Baseline (infertile): what you see when you are not fertile, so it's not actually cervical fluid. Baseline is an unchanging state of just a little bit of moisture from the vagina that will look the same day to day. It often looks like a little sheen, like what you see on your finger if you touch the inside of your cheek, or like a bit of tacky substance - kind of like flour mixed with water. You'll see baseline in what we call your "early infertile days" after your period ends but before the start of cervical fluid (or you may go straight from your period into cervical fluid), and you'll also see it in your luteal phase. It usually takes a couple cycles of observing to determine what your own baseline pattern looks like.

Point of Change (fertile): the first appearance of cervical fluid! You'll know it's CF because it will be DIFFERENT than your baseline. It's a CHANGE. You will likely see non-Peak type CF as your Point of Change, though some women go straight to Peak-type.

Non-Peak CF (fertile): the cervical fluid that you produce when your estrogen is still rising and when you’re still a little ways off from ovulating. It’s often white or beige in color and doesn’t have high water content. It usually looks some kind of variation of hand lotion.

Peak CF (fertile): what you produce when your estrogen levels are high - “peaking” - and when you’re getting close to ovulation. Peak CF is the wettest CF that you see, meaning it has the highest water content of anything you see. Peak-type will look:

• Clear, stretchy, watery, milky, stringy, lubricative, and/or slippery

• It also might have some yellow or white streaks, or spotting mixed in (this is normal to see around ovulation)

If you don't get stretchy cervical fluid - also known as "eggwhite" for the way it resembles raw eggwhite - DON'T PANIC!

There is often huge emphasis placed on seeing eggwhite, but trust me, it is not the gold standard. Sometimes there is such high water content to your CF that it eliminates the stretch factor. Milky and watery cervical fluid are just as fertile as stretchy (though keep in mind that sometimes these can also be caused by bacterial vaginosis - especially if accompanied by a fishy or metallic smell - or cervical abnormalities, especially if you see them continuously throughout your cycle and not just when you're fertile).

PEAK DAY is the last day that you see ANY quantity of Peak-type CF, not the day of the MOST CF. You'll only know you've had your Peak Day in retrospect, when you start to see a drying-up pattern going back to non-Peak and/or baseline.

Luteal mucus (infertile): After ovulation your estrogen drops, progesterone takes over, and the cervix is closed up with a thick mucus plug so nothing can get in. However, this doesn’t mean that you’ll see ONLY your baseline state during the luteal phase. You might see some other secretions that look a lot like non-Peak type CF, such as something white and thick. This comes from increased vaginal cell slough in the luteal phase, as well as little bits of the mucus plug that may shed.

A common question I see people Googling is "why do I have eggwhite cervical fluid after ovulation?" It's important to understand that unless you've confirmed that ovulation actually occurred using FAM rules - closing out BOTH Peak+3 and Temp+3 - you won't be able to confidently say you've ovulated. Ovulation pain, a period app, a positive LH test, or counting days does not qualify as confirming the big O.

However, if you DID confirm ovulation and you are seeing some fertile-looking secretions in your luteal phase, there are a few different reasons this may be happening:

• There is a small surge of estrogen halfway through the luteal phase, so if you see a resurgence of wetter secretions around days 6 - 9 of your LP, it may be due to this small estrogen rise

• At the end of your LP, progesterone is fading fast and the mucus plug over the cervix begins to break down. This can cause some wetter secretions to release from the plug. It may also be the first part of the uterine lining to flow out, which can have high water content and may even be quite slippery!

• Estrogen excess caused by chemicals that mimic estrogen (beauty products, scented home/bath/body products, cleaners, plastics, Glade plug-in candles, industrial pollutants, and more) may continue to stimulate the cervical crypts even after ovulation. Similarly, low progesterone may not be able to fully suppress cervical secretions.

• You could be pregnant: it’s quite common to see wetter, more abundant secretions in your luteal phase when you’re pregnant, even very early on (though again, please note that if you’re not practicing FAM charting, trying to determine if xyz symptom means pregnancy is dubious because you won’t know the window in which you ovulated, or where you’re actually at in your cycle. I have had clients swear they were pregnant, only to realize they either hadn’t even ovulated yet!)

HOW DO YOU SPOT FERTILE SECRETIONS/CERVICAL FLUID/CERVICAL MUCUS?

It's easy! You want to do a few things:

After using the bathroom, while you're still sitting down, touch your finger to the vaginal opening or use a flat piece of toilet paper to gather a sample. Look at what's there and feel the texture. Do this at least 3 times a day, or whenever you use the bathroom.

Notice what's on your underwear: a wet splotch? Dried crusty white stuff? A blob of something stretchy?

Notice the sensation at the vulva as you move around throughout the day. This is called walking sensation. The vulva is sensitive to as little as 5 micrograms of moisture, so learning to notice sensation is incredibly helpful! Some of us don't make a lot of cervical fluid and it can be tricky to observe via finger testing. Plus, sometimes you're at the library or giving a presentation and can't pull down your pants to look at what's there when you feel something!

You can also check at the cervix, but that involves some caveats. For beginners, stick to checking at the vulva as well as noticing walking sensation.

IS THIS NORMAL?

You may be wondering if what you're seeing is normal, so let's identify key markers of what's healthy and what's cause for seeing a doctor.

Normal vaginal and cervical secretions:

• Smell normal - like a body!

• Don't cause pain, irritation, or discomfort

• Are clear or white-beige in color

• Follow a normal pattern: baseline, non-Peak, Peak, etc

• Menstruation or spotting is normal as long as it occurs in conjunction with specific events (that is, just before your period or at the end of your period, or during ovulation)

Abnormal vaginal and cervical secretions (DISCHARGE!)

• Smell bad, fishy, or just "off"

• Come with itching, swelling, irritation, pain, or redness

• Look chunky or like cottage cheese

• Thin and grey

• Foamy or green-tinged

• Bleeding that isn't related to menstruation, ovulation, or implantation and/or is accompanied by discomfort

• Continuously seen throughout your cycle, outside of normal expected times

PS - if you have persistent BV, yeast, or other vag issues that just won't quit, you need more comprehensive care that goes beyond using creams and oral medications. Look no further than the amazing women at My Vagina and Intimate Ecology.

CRAVING MORE JUICY DETAILS?

Check out my 120-page FAM book, Learn to Chart! It goes into scintillating detail about each and every fertility sign, how to chart, how to use the 5 FAM rules to avoid pregnancy, and how to support your hormone health! 

My free intro course is also a deep dive into how FAM works and what's involved.

If you're ready to go even further, I'd love to help you learn FAM through my 1:1 program.

PLEASE LEAVE A COMMENT!

What was your biggest takeaway from this post? What questions do you have? What do you want to learn more about? I would love to know how this post lands!

SOURCES

Cervical Mucus, key to fertility – originality and wonder of Erik Odeblad’s Discoveries. Micaela Menarguez. Ph.D., Helvia Temprano. M.D.

Cohen, M. R., & Stein, I. F. (1951). Sperm Survival at Estimated Ovulation Time. Fertility and Sterility, 2(1), 20–28. doi:10.1016/s0015-0282(16)30422-8

Physiology of Ovulation. Professor Emeritus James B. Brown. https://woombinternational.org/science-of-fertility/physiology-of-ovulation/

Studies on Human Reproduction; Ovarian Activity and Fertility and the Billings Ovulation Method®  Professor Emeritus James B. Brown

Holt, E. H., Lupsa, B., Lee, G. S., Hanan Bassyouni, & H. Maurice Goodman. (2021). Goodman’s Basic Medical Endocrinology. Academic Press.

Wilcox, A. J., Weinberg, C. R., & Baird, D. D. (1995). Timing of sexual intercourse in relation to ovulation. Effects on the probability of conception, survival of the pregnancy, and sex of the baby. The New England journal of medicine, 333(23), 1517–1521. https://doi.org/10.1056/NEJM199512073332301