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
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
- 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
- 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