There are two main methods:
- With a calendar-based method, you count the days between your periods. In the week before your period and the week after it starts you’re least fertile. In the two weeks after that, you’re most fertile.
- With a symptoms-based method, apart from being aware of the days between your periods, you also check your body for signs you are ovulating. You can do this by regularly taking your temperature, or checking look and feel of the mucus coming out of your vagina.
Natural family planning methods have no side-effects and are cheap. But even with the tools available today, from apps to high-tech thermometers, they are very unreliable.The more regular your periods are, and the better you understand what happens during your cycle, the better.
But the risk of getting pregnant is still very high, and you should think carefully if you are willing to take this risk.
Failure rates
Natural family planning failure rates are comparable to the male condom in typical use (male condom: 13%, NFP: 12-14%) and are lower than the female condom in typical use (21%). Condoms are very effective.
Natural family planning may be difficult to use correctly (e.g. requires partner cooperation, etc.), allowing individual users to decide if the failure rate is acceptable. If one is able to use natural family planning correctly, failure rates are significantly lower (between 2-5%).