The Rhythm Method
You keep track of a woman’s menstrual cycle and have intercourse only during the “safe” (or infertile) days.
Typical use is difficult to estimate with this method, but with perfect use, about nine women out of 100 become pregnant in one year.
It’s free and there are no devices to deal with. And there are no side effects (except having to go without intercourse for several days before and after ovulation).
Predicting when a woman will ovulate is not easy, and sperm can live inside a woman’s body for several days. You have to keep careful track of your vaginal mucus, menstrual cycle, and/or body temperature to accurately track your fertility patterns beginning several months before you start relying on this method. Because of the difficulty of using this method, there are a lot of accidental pregnancies. Also, it doesn’t protect against STDs, including HIV.
how to get it
You will need good instruction – a class or clinician who can work with you – and several months of charting before you begin to rely on this method.