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Natural Family Planning Fact Sheet

What is natural family planning?

A woman with a normal menstrual cycle has about 8 days a month when she can get pregnant. These include the five days before she ovulates (when an egg is released), the day she ovulates, and about one to two days after ovulation.

Natural family planning (sometimes known as fertility awareness or the rhythm method) is an approach to birth control some couples use to predict when these fertile days happen. It involves paying close attention to the menstrual cycle by using methods that include:


  • Basal Body Temperature Method

  • Calendar Method

  • Cervical Mucus Method


When all three methods are used together, it is known as the symptothermal method.

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Quick Facts

Effectiveness in Preventing Pregnancy

  • Of 100 couples who use natural family planning methods each year, anywhere from 1 to 25 will become pregnant.
  • Natural family planning (NFP) can be an effective type of birth control if more than one method of natural family planning is used, and if they are always used correctly.

Use

  • A woman tracks signs such as the days of her menstrual cycle, her daily "at rest" temperature, and changes in her cervical mucus over the course of each month.

STI Protection

  • No

Clinic Visit Required

  • No, but it's a good idea to discuss natural family planning methods with a health care provider.

Basal Body Temperature Method

Basal body temperature is the "baseline" temperature when you are relaxed and rested (like when you first wake up in the morning). During ovulation(when the ovaries release an egg and you can get pregnant) the basal temperature goes up a little. You can predict the days you' are likely to be fertile if you track and record your basal temperature each day for a few months.

How It Works

Your basal temperature is typically between 96 and 98 degrees before you ovulate. After you ovulate, your temperature will rise just a bit, usually less than one degree. Such a small change is hard to detect and is best done with a basal body thermometer (available at drug stores). Write down and keep track of your temperature each day. A Basal Body Temperature ChartExit Disclaimer can help you do that.

Knowing when your temperature increases will not tell you for certain when you are fertile, but it can give a pretty good idea. You are most likely to get pregnant two to three days before your temperature peaks and the day after that. After your temperature has been higher for three days, the chances of getting pregnant drop.

Keep in mind that sperm can stay in a woman's body for several days after she has sex. If you have sex without birth control during the first part of your period, you might get pregnant.

Advantages of natural family planning

  • Natural family planning methods are safe and reasonably effective in preventing pregnancy.
  • These methods can not only help you avoid pregnancy, but they can also work if you want to become pregnant by helping to predict which days you are most fertile.
  • These methods are inexpensive and do not require a clinic visit (although it's an excellent idea to discuss your plan with a health care provider). To search for a family planning clinic near you, use the Clinic Locator.
  • Natural family planning has no side effects and does not cause problems with using medication.

Drawbacks of natural family planning

  • Your partner must agree and cooperate.
  • Natural family planning methods provide no protection against Sexually Transmitted Infections.
  • Most women don't have totally regular menstrual cycles or periods.
  • You cannot definitely know the exact days you will get pregnant.
  • Natural family planning takes time and effort each day to track days of menstrual cycle, chart temperature and cervical mucus.

Calendar Method

With the calendar method, you predict fertile days by charting and recording how long your menstrual cycles last.

How It Works

Track how many days each of your menstrual cycles last. Use a calendar and write down when each cycle starts, beginning with the first day of your period. Keep a record of how many days your cycle lasts each month.

To get the best information, you'll need to track and record how long your cycles last for at least eight months. If you can do this as long as 12 months, though, it's even better.

To predict the first day you're likely to be fertile (the most likely time for you to get pregnant if you have unprotected sex) in your new cycle:

  • You will need your menstrual cycle information from at least the past eight months, a calendar and a pen.
  • Subtract 18 days from the total days of your shortest cycle. Take that number and count ahead from the very first day of your next period (count the day your period begins).
  • Example: your shortest cycle lasted 27 days. 27-18= 9 days. On your calendar circle the date your next period starts, and beginning with that day count ahead 9 days. So if you period starts on the 2nd day of the month, you'd count ahead to the 10th day of the month. Put an "X" on the calendar for that day.

To predict the last day you're likely to be fertile in the cycle:

  • Subtract 11 days from the total days of your longest cycle. Take that number and count ahead from the very first day of your next period (count the day your period begins).
  • Example: your longest cycle lasted 29 days. 29-11=18 days. On your calendar circle the date your next period begins, and starting with that day count ahead 18 days. If your period starts on the 2nd day of the month, you'd count ahead to the 19th day of the month. Put an "X" on the calendar for that day. 

The days between the two "X's" are when you're most likely to get pregnant. If you don't want to get pregnant, then don't have sex on those days, or use birth control (like a condom, diaphragm, or cervical cap).

Keep this in mind: the calendar method can predict the days you are most likely to be fertile, but isn't always 100% accurate, especially if your cycles don't always last the same number of days. It's best to use other fertility awareness methods, too.

Cervical Mucus Method

With this method, you pay attention to the changes that happen with your cervical mucus (such as color and thickness) over the month.

How It Works

Just after your period, there a few "dry days" when no mucus is present. These are days when you aren't likely to get pregnant.

As an egg gets ready to be released (known as ovulation), more mucus is produced and it's often white or yellow in color with a sticky feel to it. These are not safe days for unprotected sex.

The most mucus is produced just before ovulation. Here, it's clear and slippery, like raw egg whites. It can be thick enough so it spreads apart on your fingers. This is the time a woman is most likely to get pregnant.

After three or four "slippery" days, less mucus is produced and anything you see is probably sticky and a darker "cloudy" color. This is usually followed by a few "dry" days before your period starts again. The time between the "slippery days' and when your period starts are days when pregnancy isn't likely to happen.

Use a tissue or your fingers to check your mucus several times each day. Note whether it's cloudy and tacky or clear and slippery. Chart the changes on a calendar. You can label days as Dry, Sticky/Cloudy, and Slippery/Clear.

Sources

Office on Women's Health

Centers for Disease Control and Prevention