Effectiveness: 75 to 97 percent; effectiveness increases if you use several methods of tracking fertility, such as calendar, cervical mucus and temperature (24 pregnancies per 100 women each year).
What is it? It's learning to recognize your fertile times by observing and documenting changes in your body as you go through your monthly menstrual cycle. To prevent pregnancy, you avoid having sex during the times you’re most likely to get pregnant, or, if you choose, use withdrawal or a barrier method of contraception during those days. It is also called the “rhythm method” or “natural family planning.” Using a combination of methods to track fertility is known as the symptothermal method.
How does it work? You may use a calendar to chart your menstrual cycle and determine when you are likely to ovulate (release an egg), along with daily documentation of cervical fluid, position and appearance of your cervix (using a speculum and mirror) and your basal body temperature. This information helps you determine the beginning and end of your fertile time.
STD protection: No; you will still need to use condoms if you are concerned about STDs.
Benefits: There are no health risks or side effects and very minimal costs. Most religions are accepting of fertility awareness as a birth control method. It increases your knowledge and awareness of your body and can increase communication with your partner.
Disadvantages: It takes time and effort every day and may be challenging, especially at first. Effectiveness depends on consistent monitoring and willingness to forego sex when you're fertile or to use a barrier method of contraception during that time. Using a calendar to chart ovulation is risky if your cycles are not always the same length.
Availability: Anyone can use this method, and instructions are widely available through books, classes and online. Tools such as calendar, thermometer, mirror and speculum are readily available.
Cost: No cost, except for basic supplies like a calendar and thermometer.
Notes: Fertility awareness is more effective when you receive careful instruction; have a partner who is also committed to the method; and have the discipline to chart your fertility signs daily. You must also be committed to abstaining, withdrawing or using barrier protection on days when you are fertile.