It seems like some people out there are pretty misinformed about how you can use the Symptothermal Method (STM), a Fertility Awareness-based Method (FABM), as natural birth control. Quite a few people have asked if STM is the same as the Rhythm Method—AKA an outdated, ineffective method that’s caused a whole lot of unplanned pregnancies! Come on, do you really think that’s what we’re all about? :)
Granted, if you’re not familiar with FABMs, the idea of having unprotected sex without being on the pill or another conventional birth control may cause some anxiety, but we're here to let you in on something: The Symptothermal Method is an effective method of birth control — 99.6% effective, when used correctly (1)! It only takes a few minutes a day, and it's totally natural and free (other than the cost of a basal body temperature thermometer, I guess). Plus, it's fascinating to learn about how your body works and how you can work WITH your body to achieve your fertility goals, rather than leaving that up to synthetic hormones or a foreign object inserted in your body. Also, if you do decide you want to get pregnant at some point, having better knowledge and awareness about your body could make conceiving easier (5).
Kindara makes using STM as birth control easier by providing a robust tool to record and visualize your data so you can interpret it easier. But how do you use STM as birth control? You need to know about your cervical mucus and basal body temperature, and maybe cervical position too. Most importantly, you and your partner need to be 100% dedicated to following the 4 rules of using STM as birth control (explained below).
First, some basics:
During your cycle, there are typically 6 days when you are fertile (2). This is due to the combined fertility of a couple: an egg will only survive for 12-24 hours after being released from the ovary (4), sperm can survive in fertile cervical mucus for up to 5 days (4). In other words, 5 days for the sperm lifespan plus the day of ovulation is 6 days total.
The quantity and quality of your cervical mucus is key to whether you are fertile or not. Without cervical mucus, the vagina is very acidic to protect against infection (6). Because sperm requires a more alkaline environment (such as seminal fluid) to survive, it typically will not survive in the vagina for more than 1-2 hours if cervical mucus is not present (7).
Important Note: While this is a great summary, before relying on STM as birth control, we recommend you do the following:
- Chart your signs for at least a few cycles so you have a clear understanding of your fertility signs and how they change throughout your cycle (3).
- Read a book about STM, like Toni Weschler's Taking Charge of Your Fertility, to fully understand the science behind this method.
- Take a class and consult with a fertility awareness instructor for individual review of your charts and technique so that you understand EVERYTHING about the method.
Pregnancy outside of the fertile window is not known to happen (2), but for this method to work, you need to be able to identify that fertile window to avoid pregnancy.
So, here they are - the 4 rules of using STM as birth control.
1) First 5 days rule—You are generally considered infertile the first 5 days of your menstrual cycle, unless you have ever had a cycle that was less than 25 days long.
During the first 5 days of your cycle, your body probably isn't producing fertile cervical mucus, and ovulation is likely too far off for sperm to be able to survive until it occurs. So, you are considered infertile during that time. This rule applies regardless of how many days your period lasts. Any bleeding after the first 5 days of your cycle should be considered fertile, as the blood could mask fertile cervical mucus (3).
- 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.
- If any of your cycles in the past 12 months have been less than 25 days, you should consider yourself infertile for only the first 3 days of your cycle (3). This is to avoid the risk of getting pregnant due to early ovulation. Also, those who are beginning to experience signs of menopause should not rely on this rule, as they can experience major hormonal changes that could cause early ovulation.
- If you experience spotting after your period ends, don’t assume you’re still infertile. Some women experience ovulation spotting or spotting just before or during ovulation (9). Ovulation spotting, which is thought to be due either to a surge in estrogen levels or as a result of the egg rupturing through the follicle as it is released from the ovary, is actually considered to be very fertile cervical mucus (3).
This picture shows a section of the chart that is Considered Infertile
2) Dry day rule—You are generally considered infertile the evening of any day you observed that you had no cervical mucus (6).
If there’s no cervical mucus, you’re not considered fertile (6). However, you need to wait until the evening to have unprotected sex to make sure your body doesn’t produce fertile CM during the day. FYI - arousal fluids and lubricants do not provide an environment in which sperm can survive, unless of course you're using a lubricant specifically made for sperm capacitation (but you're prooobably not doing that if you're using FAM as birth control, right??)
If you only experience one or two consecutive days of sticky CM and then revert back to dry days, you are considered safe again the evenings of each dry day (3). But if you ever observe creamy or egg white CM, you should NOT consider yourself safe even if you have a dry day afterward.
Sometimes, residual semen from intercourse can mask the presence of CM. So, if there's any semen present in the vagina the day after intercourse, you should consider yourself potentially fertile, to be safe (to eliminate semen from the body so this doesn't happen, you can do Kegels exercises after intercourse).
Note: The vagina is a mucous membrane, like your mouth, so most people will almost always experience a slight moistness at the vaginal opening. You're still considered dry if there's no true CM present. For more on cervical mucus, check out this blog.
This picture shows a section of the chart that is Considered Infertile.
3) Peak plus 4 rule—You are generally considered infertile the evening of the 4th day after your most fertile cervical mucus and once your CM has become infertile again, and you have observed a clear BBT shift.
As you approach ovulation, your CM will generally progress from Dry --> Sticky --> Creamy --> Eggwhite --> Watery as it becomes more fertile. The wetter your CM, the more fertile it is. After ovulation, your CM will begin to dry up. The last day of wetness that you experience before you begin to dry up is your Peak Day - generally the point during your cycle at which you are most fertile. Note that the Peak Day is your LAST day of wetness, and not necessarily the day of the MOST wetness; in other words, if you have lots of watery CM on Monday, then a little watery CM on Tuesday, and then sticky CM on Wednesday, Tuesday would be your Peak Day.
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. This is because it's possible that you won't begin to ovulate until 2 days after your Peak Day (3). At ovulation, it's possible to release two eggs within 24 hours of each other; this is how fraternal twins are conceived, and it's said to happen 5-10% of the time (10)! And since each egg can live a maximum of 24 hours, this adds up to 4 days after the Peak Day.
Exceptions: Those with Polycystic Ovarian Syndrome or other hormonal disorders can sometimes experience ‘false peaks’ in which their CM builds up from infertile or less fertile (sticky) to fertile (egg white/watery) and back to infertile again, but ovulation does not occur (3). This is why it’s especially important to keep track of your BBT as well as your CM, so that you can confirm ovulation.
This picture shows a section of the chart that is Considered Infertile, notice the "P" for Peak Day and the "Plus 4 Rule" shows as numbers 1-4 above.
4) Temp plus 3 rule—You are generally considered infertile the evening of the 3rd day after your BBT shift.
A BBT shift that is sustained for at least 3 days confirms that ovulation has occurred (3). You need to make sure the BBT shift is sustained for at least 3 days because it's possible that you won't ovulate until 24 hours after your temperature shift, and again, it's possible to release 2 eggs within 24 hours of each other. Also, you'll want to ensure that the rise in your temperature was due to ovulation and not to something else, such as drinking alcohol the night before, fever, lack of sleep, etc. Look for 3 consecutive temperatures above your coverline (12). Once a sustained BBT shift has occurred (and following the other rules), you are considered infertile for the rest of your cycle.
This picture shows a section of the chart that is Considered Infertile. Also, notice the numbers 1-3 on the Temperature Line after "Peak Day" to showcase the Temp Plus 3 Rule.
So, there you have it! Once you get the hang of tracking your fertility signs, you can have unprotected sex during your infertile days, and either abstain or use a barrier method of protection, such as condoms, during your fertile days. (Of course, it’s always a good idea to use condoms with new partners to protect against STIs, whether you’re in your fertile window or not!) If in doubt, assume you’re fertile.
Plus, check out this cool video we made about using FAM as natural birth control. Feel free to show it to your skeptical or misinformed friends!
- Planning, N. F. (1984). Natural Family Planning.
- Wilcox, A. J., Dunson, D., & Baird, D. D. (2000). The timing of the “fertile window” in the menstrual cycle: day specific estimates from a prospective study. Bmj, 321(7271), 1259-1262.
- Weschler, Toni. (2015). Taking Charge of Your Fertility: The Definitive Guide to Natural Birth Control, Pregnancy Achievement, and Reproductive Health.
- University of California San Francisco. (n.d.). Conception: How It Works. Health.
- Gnoth, C., Godehardt, D., Godehardt, E., Frank‐Herrmann, P., & Freundl, G. (2003). Time to pregnancy: results of the German prospective study and impact on the management of infertility. Human reproduction, 18(9), 1959-1966.
- FACTS. (n.d.). Sympto-Thermal Method.
- Suarez, S. S., & Pacey, A. A. (2006). Sperm transport in the female reproductive tract. Human reproduction update, 12(1), 23-37.
- Thijssen, A., Meier, A., Panis, K., & Ombelet, W. (2014). ‘Fertility Awareness-Based Methods’ and subfertility: a systematic review. Facts, views & vision in ObGyn, 6(3), 113.
- American Pregnancy Association. (n.d.). Ovulation Symptoms.
- American Pregnancy Association. (n.d.). Ovulation: Frequently Asked Questions.
- Su, H. W., Yi, Y. C., Wei, T. Y., Chang, T. C., & Cheng, C. M. (2017). Detection of ovulation, a review of currently available methods. Bioengineering & translational medicine, 2(3), 238-246.