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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
Fertility awareness is done to help a
woman learn when she is likely to ovulate. This information can help a
To use fertility awareness as a birth control
Before you use fertility awareness as
a method of birth control, record three or four of your menstrual cycles to find your
pattern of ovulation. If you are trying to not become pregnant during this
time, use a method of birth control that does not affect ovulation (such as a
condom, diaphragm, or the copper
intrauterine device [IUD]) or do not have sex.
Basal body temperature is checked using a special oral thermometer marked
in fractions of a degree so you can see even small changes in temperature
better than with an ordinary thermometer. Easy-to-read digital thermometers can
be found in most pharmacies or at family planning clinics. Do not use a digital
ear thermometer for this method.
For fertility awareness to work well,
it is best to use all of the following methods together.
Record the dates of your
menstrual periods for 6 to 8 months. See if your menstrual cycle is regular and
how many days it is. If your cycle is regular and about 28 days long, you are
most likely to ovulate 14 to 15 days after menstrual bleeding begins.
To find the first day that you are likely to be fertile, take 18 away
(subtract) from the number of days in your shortest menstrual cycle. Your first
fertile day should be that many days after your menstrual bleeding begins. For
example, if your shortest menstrual cycle is 26 days long, you would subtract
18 from 26 to get 8; your first fertile day would then be the 8th day after
menstrual bleeding begins.
To find the last day that you are
likely to be fertile, subtract 11 from the number of days in your longest
menstrual cycle. Your last fertile day should be that many days after your
menstrual bleeding begins. For example, if your longest menstrual cycle lasts
31 days, you would subtract 11 from 31 to get 20; your last fertile day would
then be the 20th day after menstrual bleeding begins.
live in your vagina 3 to 5 days after sex.
The calendar method of birth control is not the best
choice for women who have short, long, or irregular menstrual cycles. For this
reason, the calendar method alone is never recommended for birth control. It
must be used in combination with other birth control methods.
On the first day of
your period, move the ring to the red bead (day 1) on the CycleBeads. Count
each day as one bead. On days 1 to 7, you can have unprotected sex. On days 8
to 19, do not have sex or be sure to use another method of birth control to
avoid pregnancy. From day 20 to the end of your cycle, you can have unprotected
sex. All brown beads are days when you are not likely to become pregnant. All
white beads are days you are likely to become pregnant. The dark brown bead
marks day 26 and the last brown bead before the red bead is day 32. The SDM
works best for women who have cycles between 26 and 32 days long.
temperature every morning for several months just after you wake up. Do it
before eating, drinking, or doing any other activity. Use a special ovulation
thermometer or digital thermometer that shows tenths (0.1) of a degree. Your
temperature may be taken orally or rectally, but be sure to use the same
location and the same thermometer each time. Leave the thermometer in place for
a full 5 minutes. Record your temperature, then clean the thermometer and
put it away. Any activity can change your basal temperature. Record your
temperature on a chart or graph. 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. Ovulation usually causes your BBT to rise by
0.4°F (0.2°C) and to stay high for over a week.
want to become pregnant, have sex every day or every
other day from your first fertile day until 3 days after your BBT rises.
If you do not want to become pregnant, do not have
sex or be sure to use another method of birth control from the end of your
menstrual period until 3 days after ovulation. After your temperature rises and
stays high for 3 full days, your fertile days will be over. Your temperature on
these 3 days should stay higher than on any of the other days in that
put one finger into your
vagina and record the amount, color, and thickness (or
thinness) of the mucus. Test the "stretchiness" of the mucus by putting a drop
of it between your finger and thumb. Spread your finger and thumb apart and see
if the mucus stretches.
After your 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. It may stretch about
1 in. (2.5 cm) before it
If you want to become pregnant,
have sex every day or every other day from the day you see your cervical mucus
becoming clear and stretchable until the day it becomes cloudy and sticky. Do
not test your mucus right after sex, since semen may be mixed with it.
If you do not want to become pregnant, do not have
sex or be sure to use another method of birth control from the day your
cervical mucus becomes clear and stretchy until the 4th day after it becomes
cloudy and sticky.
Another 2-day method of checking your cervical
secretions can be done. Every day of your cycle, ask yourself if you have
secretions today and did you have secretions yesterday. For all days that you
answer "yes" to one of these questions, it is likely that you are fertile and
can become pregnant if you have unprotected sex. If you answer "no" to both
questions on any day, you are not likely to become pregnant.
If you are using a home
ovulation kit, follow the instructions on the kit exactly.
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, abdominal pain, and mood changes). You may have any of the
following physical signs of ovulation:
If you do not want to become
pregnant, do not have sex or be sure to use another method of birth control for
5 days before ovulation may occur and on the day of ovulation.
Keeping a record of your menstrual cycle
(fertility awareness) takes time and effort every day, but it is important to
do so to find out your most fertile time.
You may have an unplanned pregnancy using
fertility awareness. To use these methods to prevent a pregnancy, do not have
sex during the entire time that an egg can be fertilized, including 5 days
Generally, your most fertile days begin
5 days before ovulation and end on the day of ovulation. Pregnancy can
occasionally occur after ovulation, but it is less likely than in the days
If your menstrual cycle
is 28 days long, you are most likely to ovulate about 14 to 15 days after
menstrual bleeding begins.
If you do not want to become pregnant,
the calendar method of birth control is not the best choice for women who have
short, long, or irregular menstrual cycles. For this reason, the calendar
method alone is never recommended for birth control. It must be used in
combination with other birth control methods.
The SDM works best for
women who have cycles between 26 and 32 days long. If you have more than one
cycle in one year that is shorter than 26 days or longer than 32 days, you need
to use another method to avoid pregnancy.
body temperature (BBT) usually drops about 0.4°F (0.2°C) below your normal
temperature 1 to 2 days before ovulation. It then increases the same amount or
more above your normal temperature 1 to 2 days after ovulation and stays high
until just before your menstrual period begins. Since the rise in BBT does not
occur until after ovulation, it is possible to become pregnant if you have sex
just before or during ovulation.
Many women do not have a regular
temperature pattern, so it can be hard to use this method to know when
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. It may stretch about
1 in. (2.5 cm) before it
For the 2-day method of checking your cervical secretions,
ask yourself if you have secretions today and did you have secretions
yesterday. For all days that you answer "yes" to one of these questions, it is
likely that you are fertile and can become pregnant if you have unprotected
sex. If you answer "no" to both questions on any day, you are not likely to
Home ovulation tests measure
the amount of luteinizing hormone (LH) in the urine and display the results on
a test strip or a small computer unit.
Many women have
symptoms such as breast tenderness, swelling of the
vulva, bloating, belly pain on one side, or increased
sexual desire around the time of ovulation.
is most effective when all the methods are used together. The number of
unplanned pregnancies is 25 out of 100 women who typically use these methods.
If you have had a baby in the past 6 months or if you have an
irregular menstrual cycle, it may be hard to use this method to know when
Fertility awareness methods will
not work very well:
The calendar method will
not work very well if:
The BBT method
will not work well if you:
cervical mucus method will not work very well if you:
The results of hormone
monitoring may not be correct if you do not follow the home ovulation kit
changes the results of one of the methods also changes the results of the
Other Works ConsultedFritz MA, Speroff L (2011). Female infertility. In
Clinical Gynecologic Endocrinology and Infertility, 8th
ed., pp. 1137–1190. Philadelphia: Lippincott Williams and Wilkins.Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.
December 7, 2011
Sarah Marshall, MD - Family Medicine & Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology
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