What is the Sympto Thermal Method? A Natural Birth Control You’ve Likely Never Heard Of

Fertility Awareness

This post is an overview of the 4 Sympto Thermal Method rules of what practicing this method involves, and is intended to aid your decision if this method could be an option for you!

What Is The Sympto Thermal Method?

The Sympto-Thermal Method is a natural form of fertility awareness, practiced by observing and charting two of our body’s fertility signs — basal body temperature and cervical fluid — everyday to determine which days will lead to pregnancy and which days will not.

It is hormone-free, non-intrusive and has been found to be 99.4% effective with perfect use. 

Before we get into all the specifics and rules, a little disclaimer; this blog is intended as an introduction and starting point to help you decide if FAM is right for you and in no way substitutes learning a method thoroughly! For additional details, please see our course below.

Let’s go…

The 4 Rules


First 5 Days Rule (First 3 Days Rule if Charting Less Than 1 Year)

If you’re in your first year of charting, you are generally considered infertile the first 3 days of your menstrual cycle.

If in one year, you have never had a cycle that was less than 25 days long, you are generally considered infertile the first 5 days of your menstrual cycle.

Two things to note here: 

  • This rule applies only if you observed a clear BBT shift 12 to 16 days prior to the start of your cycle. This confirms that the bleeding you experience is your period and not abnormal bleeding or ovulation spotting.
  • For pre-menopausal women, the rule is the first 3 days regardless because hormonal flucuations during the years appraching menopaus can result in early ovulation.

Dry Day Rule

You are generally considered infertile the evening of any day you observed that you had no cervical fluid.

However, you need to wait until the evening to have unprotected sex to make sure your body doesn’t produce potentially-fertile cervical fluid during the day. 

If you only experience one or two consecutive days of sticky cervical fluid and then revert back to dry days, you are considered safe again the evenings of each dry day.  But note that this means if you ever observe creamy or egg white cervical fluid, you should NOT consider yourself safe even if you have a dry day afterwards.

Temp +3

You’re considered infertile after 6 P.M. on the evening of your third high temperature above your coverline.

Here’s the reason why: 

You need to wait for three consecutive high temperatures above your coverline because you might not ovulate until twenty-four hours after the rise. Then, 10 percent of the time, women release two eggs at ovulation —requiring a total of three days of high temperatures to confirm that you’re not fertile.

Peak +4

You are generally considered infertile the evening of the 4th day after your most fertile cervical fluid and once your CF has become infertile again, and you have observed a clear BBT shift.

You need to wait until the evening (6 PM or later) of the fourth day after your Peak Day until you can consider yourself infertile.

Here’s the reason why:

It’s possible that you won’t begin to ovulate until two days after your Peak Day. At ovulation, it’s possible to release two eggs within 24 hours of each other (this is how fraternal twins are conceived), and since each egg can live a maximum of 24 hours, this adds up to 4 days after the Peak Day.

Cervical fluid and BBT patterns don’t always line up exactly. If yours don’t, postpone intercourse or use a barrier method until you’ve confirmed ovulation by both fertility signals.

** For Premenopausal Women

Hormonal changes during the years approaching menopause can result in early ovulation, therefore they’ll need to revert back to the first 3 day rule.

** For Postpartum Women

There are additional rules and nuances for practicing the sympto-thermal method postpartum.

How Much Time Does It Take To Learn This Method?

Shorter than you’d probably expect! The rules can seem a bit confusing and overwhelming in the beginning, but don’t worry, it doesn’t take long before you commit these rules to memory.

Some women will feel confident reading the relevant chapters in Taking Charge Of Your Fertility, others will prefer an in person workshop, or an online course.

After learning the method, it usually takes two to three cycles observing and tracking to feel confident enough to use this method as birth control. After that, charting usually takes just a few minutes each day; 1 minute to take your temperature upon waking in the morning and another couple of minutes to record your fertility signs in an app.

Where Can I Learn The Sympto Thermal Method?

If you are interested in learning this method, there is a growing number of passionate fertility awareness educators offering in person and online courses in their method of choice.

I hope this article was informative and educational. Here’s to learning we have more available options than we previously knew of (which is always a good thing) !


Natural Birth Control Introductory Articles

What is fertility awareness?
Your Natural birth control questions answered
8 mistakes to avoid when using natural birth control


FAM is 99.4% effective when used correctly. P.Frank-Herrman et al. Human Reproduction 2007; 22:1310-1319.

Timing of sexual intercourse in relation to ovulation. Wilcox et al. New England Journal of Medicine 1995; 333:1571-1521. 

The 4 Rules of charting for birth control:

Stanford et al. Obstetrics and Gynecology 2002; 100:1333-1341.

Grimes et al. Contraception 2005; 72:85-90.

Freundl et al. The European Journal of Contraception and Reproductive Health Care 2010; 15:113–123.

Robinson et al. Current Medical Research and Opinion 2007; 23:301–306.

Bigelow et al. Human Reproduction 2004; 19:889-892.

P.Frank-Herrmann, et. al. The European Journal of Contraception and in Reproduction Health Care 2010; 15:113-123

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Wonderful Within is a blog designed to educate and empower women from within. We talk all things wonderful, including: menstrual cycles, periods, charting, fertility awareness and women’s health and wellness choices.

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