Clinical Reference Systems: Pediatric Advisor 10.0
Natural Family Planning
Natural family planning is a way to practice birth control
without using drugs or contraceptive devices. Two methods
of natural family planning are the rhythm method (also
called the calendar method) and the withdrawal method. (The
withdrawal method is not recommended because it frequently
results in pregnancy.)
RHYTHM METHOD (CALENDAR METHOD)
- Your menstrual cycle
During each menstrual cycle, two events occur: (1) you
have your period (menstruation) and (2) you release an
egg from one of your ovaries (ovulation). When you are
ovulating you are fertile, which means you have a very
high risk of getting pregnant.
The first day of your period is the first day of your
menstrual cycle. The day before your next period begins
is the last day of your menstrual cycle. The average
menstrual cycle is 21 to 35 days long.
If you want to use the rhythm method for birth control,
you must understand how your body works, keep a very
accurate record of your menstrual cycle, and do some
calculations. Your goal is to determine how long your
menstrual cycles are and when you ovulate.
- Keeping a calendar
On a calendar mark the days your periods start. From
this information you can calculate the number of days in
your menstrual cycle. For example, if you started your
period on December 10, December 10 was the first day of
your menstrual cycle. If your next period began
January 7, the length of your menstrual cycle was 28
days (22 days in December and 6 days in January). Now,
you begin again, with January 7 as day 1 of your next
Menstrual cycles often vary somewhat in length from
month to month. For this reason you need to keep a
record of your menstrual cycle for 3 to 6 months. You
will then have a pretty good idea of how long your
shortest and longest cycles are. You will use this
information to calculate the days when you are most
likely to ovulate and get pregnant if you have sexual
- When NOT to have sex
Once you know the lengths of your shortest and longest
menstrual cycles you can figure out when you have a high
risk of getting pregnant. You do this by subtracting
18 days from your shortest cycle and 11 days from your
longest cycle. From the results of these calculations
you will know when you are most fertile. The result of
the first calculation is the day you should stop having
sexual intercourse. The result of the second
calculation is the day when you can start having sex
For example, let's say your shortest cycle in 8 months
was 25 days and your longest cycle was 30 days.
Subtract 18 from your shortest cycle and 11 from your
longest cycle. Here's how the calculations look:
25 (shortest cycle) 30 (longest cycle)
These calculations mean that from the 7th to the 19th
days of your cycle you should NOT have sex. You will
ovulate sometime during these days in your cycle and
have a high risk of getting pregnant. Remember that the
first day of your period is "day 1" of your menstrual
cycle. So in this example you are at high risk of
getting pregnant 7 days after the start of your period
and for the next 12 days. For example, if your next
period starts on February 5 (day 1), then you should not
have sex from February 11 (day 7) to February 23
- Advantages of the rhythm method
- This method helps you calculate which days of the
month you are most likely to get pregnant.
- This method helps you know more about your menstrual
cycles and your body.
- You may safely and inexpensively prevent pregnancy if
you follow the rhythm method properly.
- This method is accepted by most religions that oppose
other contraceptive methods.
- Disadvantages of the rhythm method
- If you use this method of birth control, you can have
sex only during certain days of your menstrual cycle.
Because you cannot have sex whenever you want to this
method requires a lot of self-control by you and your
- You must keep detailed records of many (8) menstrual
cycles before you use this method for birth control.
You must continue to keep track of your cycles while
using this method.
- If your periods (cycles) are irregular, you cannot
use this form of birth control because you cannot
safely calculate when you are fertile.
- This method is only 70 percent reliable for
preventing pregnancy, even in women with predictable
cycles. This means 30 out of 100 couples (or 3 out
of 10) will have pregnancies if they rely on this
method for a year.
- You are not protected against sexually transmitted
diseases (STDs). To protect yourself against STDs,
you must use a condom every time you have sexual
WITHDRAWAL METHOD (ALSO CALLED COITUS INTERRUPTUS)
We do NOT recommend withdrawal as a method of birth control.
Many people believe that if a man and a woman are having
sexual intercourse and the man pulls his penis out of a
woman's vagina before he ejaculates, the woman will not get
pregnant. (Ejaculation is the release of sperm.) However,
this is NOT TRUE. There have been many, many unwanted
pregnancies as a result of this approach to birth control.
In reality, some sperm are released from the penis into the
vagina BEFORE a man ejaculates. That is, by the time he
pulls out, some sperm are already on their way to an egg.
The withdrawal method is not considered to be an effective
form of natural birth control. Use of this method is
strongly discouraged if you want to prevent pregnancy.
CALL YOUR PHYSICIAN DURING OFFICE HOURS IF:
- You have any questions or concerns.