This primer was prepared to illustrate the use of the Sympto-Thermal Method for reasons other than trying to achieve a pregnancy.
Many of you are already aware of and benefitted from the use of Sympto-Thermal and other natural fertility methods for purposes of achieving a pregnancy. Did you know that it is just as effective as natural birth control? You need only follow a few simple rules that take into account you and your partner’s combined fertility (while you are really only fertile for 24-48 hours, sperm can live up to 5 days under ideal conditions – therefore combined fertility is important).
The First 5 Days Rule
This rule states that you are safe the first 5 days of your cycle if you had a clear temperature shift 12-16 days before. This is irrespective of how long your period actually is. Evidence of a clear temperature shift in the previous cycle is the key to this rule. Some women experience spotting/light bleeding around the time of ovulation – literally from the egg bursting from the ovary – which can be mistaken for a period. This very scenario is the likely culprit for those stories you hear of women becoming pregnant during their period. For women with short cycles (as in, 25 days or less), you will need to have a wider margin of safety – in your case, the first 3 days are safe.
The Dry Day Rule
This rule states that you are safe the evening of every dry day before ovulation. ˝Dry day˝ means that you observed NO cervical fluid at any point during the day. Cervical fluid is different than the slight dampness/moistness that is always present, by the way. You can tell the difference by the fact that it quickly dissipates from the finger – true cervical fluid will not. If this is the only moisture that you encounter that day, than you are considered ˝dry.˝ Note: Even if you observed sticky cervical fluid*, which is not conducive to sperm survival, you must consider yourself potentially entering your fertile phase just to be on the safe side.
The Temperature Shift Rule
This rule states that you are safe the evening of the 3rd consecutive day that your temperature is above the coverline (meaning, ovulation has been confirmed).
The Peak Day Rule
This rule is related to the Temperature Shift Rule. It states that you are safe the evening of the 4th consecutive day after your peak day. The peak day is the last day that you produce fertile quality cervical fluid (resembling raw eggwhite) or have a lubricative vaginal sensation. It’s called the ˝Peak Day˝ because it’s the peak day of fertility – occuring either the day before or the day of ovulation. Any wetness will dry up as a result of the progesterone-dominated luteal phase. If you happen to see wet cervical fluid or feel lubricative vaginal sensation again within the 4-day count prescribed by the Peak Day Rule, you will need to wait until the wetness subsides to re-establish the true peak day and then start counting again. The peak day will almost always be the day before your temperature shifts and that will ultimately confirm when you’ve finally ovulated.
So, those are the rules for using the Sympto-Thermal Method to avoid a pregnancy. The guiding principle with these rules is that if you encounter any ambiguity, be conservative. If you fudge the rules at any point, you run the risk of a pregnancy precisely because you ARE approaching or are in the most fertile phase of your cycle. And if an unplanned pregnancy is a big deal for you and your family, don’t fudge the rules 
*Sticky cervical fluid can be: pasty, tacky, crumbly, gummy, springy and dry like rubber cement. It is usually white or yellow. The vaginal sensations which accompany sticky cervical fluid are usually dry or sometimes sticky. The point is that you will not feel the sensation of wetness.
For additional information, see Taking Charge of Your Fertility by Toni Weschler.
Editor’s Note: For more information on the effectiveness of the Sympto-Thermal Method, here are the results of a study showing a failure rate of 0.4 pregnancies per 100 women – which is comparable to The Pill. This is when the user abstains during her fertile phase. For couples who opted to remain sexually active during the woman’s fertile phase (using a barrier method), the effectiveness fell to 0.6 pregnancies per 100 women.
Other posts on fertility charting:
Thanks for posting this. Sometimes people get the wrong idea about nfp. I think more people would use nfp if they were more aware of what it is and how it works.
I definately agree. If the same outcome can be achieved naturally, why not do that? People had some great comments about using a method like this for birth control on the FB page when we were discussion it. I was happy to see so many people either using it currently or now considering it. It’s healthy, effective. One woman mentioned that it’s like having a honeymoon period every month – presumably because there are a few days where they can’t
Sort of an absence makes the heart grow fonder effect 