Fertility awareness (also called natural family planning or periodic abstinence) is a way to check the changes your body goes through during a menstrual cycle . This information can help you learn when you ovulate. You can then time sexual intercourse to try to become pregnant or to try to avoid pregnancy.
A woman is usually able to get pregnant for about 6 days each month, which is the day of ovulation and the 5 days before it. On average, ovulation occurs 12 to 16 days before the menstrual period begins. So ovulation would occur on about day 10 of a 24-day menstrual cycle, day 14 of a 28-day cycle, or day 21 of a 35-day cycle. Sperm can live for 3 to 5 days in a woman's reproductive tract, so it is possible to become pregnant if sex occurs 2 to 3 days before ovulation.
For fertility awareness to be used as birth control, either you must not have sex or you must use a barrier method of birth control (such as a diaphragm or condom) for 8 to 16 days of every menstrual cycle. To use fertility awareness, you must prepare each month, be familiar with your body changes, and talk with your partner about your cycle.
Fertility awareness is not the best method of birth control to prevent a pregnancy. The number of unplanned pregnancies is 25 out of 100 women who typically use fertility awareness. But this method can be very helpful to time when to have sex to become pregnant.
There are several basic methods for determining the time of ovulation. For fertility awareness to be most effective, you need to use all of these methods in combination. Check your body changes using these methods for several months before using them to avoid pregnancy.
Calendar (rhythm) method. For the calendar method, you guess your next ovulation time after recording your last few months of menstrual cycles. From the record, you guess which days of the month you are most likely to ovulate (be fertile). Your fertile days start 5 days before ovulation and end on the day of ovulation. This method works if your menstrual cycle is regular, because then you will ovulate on a certain day of the month. But very few women have regular 28-day cycles. Even women who have regular cycles can have irregular periods from time to time. Also, a woman does not always ovulate right in the middle of her cycle and is more likely to ovulate between 9 and 17 days before her next period. So the calendar method alone is not the most effective method of guessing when you might be ovulating.
Standard days method (SDM). The SDM works best for women who have cycles between 26 and 32 days long. You usually use a special colored string of beads (CycleBeads) to keep track of your cycle if you use this method. The red bead is the first day (day 1) of your period. Count each day as one bead. A dark brown bead marks day 26 and the last brown bead before the red bead is day 32. If you have more than one cycle in one year that is shorter than 26 days or longer than 32 days, you may need to use another method to avoid pregnancy.
Basal body temperature (BBT) method. Basal body temperature (BBT) is the lowest body temperature a healthy person has during the day. A woman's hormone levels during her menstrual cycle naturally cause her BBT to fall 1 to 2 days before ovulation and then rise 1 to 2 days after ovulation. By carefully measuring and recording your BBT every morning before you get out of bed, you may be able to guess the day you will ovulate. Use a tracking chart with either Fahrenheit temperatures(What is a PDF document?) or Celsius temperatures(What is a PDF document?) to keep track of your temperature for a few months.
Cervical mucus method (Billings method). The amount, texture, and look of mucus made by your cervix changes during your menstrual cycle. By watching, feeling, and recording this information for several cycles, you may be able to guess when you will ovulate.
- Right after your menstrual period, you will not have much cervical mucus and it is thick, cloudy, and sticky.
- Just before and during ovulation, you will have more cervical mucus and it is thin, clear, and stringy.
Hormone monitoring. Home ovulation kits can be used to help you learn the most fertile days of your menstrual cycle. These tests check the level of luteinizing hormone (LH) in your urine. You use a dipstick or test strip, dip it in your urine, and read the level on the strip or put the strip in a small computer unit that shows the level of LH. The computer can tell you when your most fertile days are.
Combined (symptothermal) method. This method uses some of the other methods all at once to tell you the most fertile days of your cycle. You check your basal body temperature, the changes in your cervical mucus, and a hormone test, and you watch for signs of ovulation (such as breast tenderness, belly pain, and mood changes). The physical signs of ovulation help you learn when you ovulate.