Natural family planning is contraception achieved by knowing on what days of your menstrual cycle you're most likely to get pregnant and avoiding intercourse on those days. With natural family planning, you have a birth control option that's not tied to taking medicine, using a barrier device or having surgery.

Natural family planning can work if you choose a method you can follow diligently.

To help decide if natural family planning is the appropriate method for you, find out what it's all about.

Natural family planning centers on fertility awareness. To determine when you're fertile, you monitor physical signs such as your body temperature when you first wake up in the morning (basal body temperature) and cervical mucus consistency. Knowing when your fertile phase occurs helps you avoid intercourse when pregnancy is most likely to take place. By recognizing, charting and understanding certain physical signs, you can predict your fertile phase with a high level of accuracy.

Natural family planning hinges on your understanding of your menstrual cycle. Each month several follicles begin to develop in one of your ovaries. Follicles are tiny sacs, each containing a single immature egg. One follicle eventually grows larger than the others and contains a single mature egg — the one your body intends for fertilization.

Meanwhile your ovaries secrete estrogen from the dominant follicle. Estrogen thickens the lining of your uterus (endometrium) to prepare for implantation if the egg is fertilized. Soon after, the follicle ruptures and releases the egg (ovulation).

The egg released at ovulation enters your fallopian tube on its way to the uterus. During the egg's journey, a sperm may fertilize it. If fertilization occurs, the egg implants itself in the lining of your uterus and menstruation doesn't occur. If the egg isn't fertilized, menstrual flow begins about two weeks later.

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For many women, menstrual cycles regularly occur about every 28 days. For other women, cycles may occur every 21 to every 35 days. Natural family planning relies heavily on your knowing the frequency and variations of your cycle.

You must also be alert to specific changes to your body, such as shifts in your body temperature and changes in the consistency of your cervical mucus. You can track these changes using one of many different methods:

• Calendar method. This method simply consists of recording the time of your monthly menstrual cycles. It may be difficult to determine your fertile days by the calendar method alone because your menstrual cycle may not be the same each month.
• Temperature method. Your basal body temperature rises slightly on the day of ovulation and remains at that level until your next period. When using the temperature method, you take your temperature orally and then record it every morning. You may be able to discern your fertile phase based on patterns created over time by your recorded temperatures.
• Cervical mucus method. Another change that regularly occurs during your menstrual cycle is the consistency of your cervical mucus, a jelly-like substance produced in your cervix. When using the cervical mucus method, you check your cervical mucus using your finger or a piece of toilet paper and record its consistency every morning. Your cervical mucus is clear and slippery — with a strong resemblance to raw egg white — when you're most fertile. Whenever your cervical mucus has this consistency, you're fertile.
• Cervical position and dilation method. Your cervix noticeably opens and changes position at the time of ovulation. When using the cervical position and dilation method, you check your cervical position using your finger. During ovulation, your cervix is slightly higher, softer and more open than it normally is. You may be able to discern your fertile phase based on patterns created by your recorded positions.
• Symptothermal method. The symptothermal method uses all four techniques — calendar, temperature, cervical mucus, and cervical position and dilation — at the same time. The symptothermal method provides a more accurate prediction of your fertile phase because signs noted while using one method may confirm those noted when using another method. Natural family planning may be most effective when you choose the symptothermal approach.
• Standard days method. This method requires abstaining from unprotected intercourse on days eight through 19 of your menstrual cycle. These are the days you're most likely to conceive. If you abstain from intercourse or use a backup method of birth control during that time, the standard days method can be highly effective. Marketed as an aid to this method is a bead system — called CycleBeads — that allows you to easily keep track of the days you’re fertile versus those you aren't. Unfortunately, for women in their late 30s or early 40s, cycles tend to shorten. In that case, days five through eight may be within your fertile phase.
• 'TwoDay' method. With the TwoDay method, you pinpoint your fertility based on secretions from your cervix. Cervical secretions include anything you perceive as coming from your vagina except for menstrual bleeding or semen. It's a simpler method than the others and requires only that you ask yourself two questions: Did you notice any cervical secretions today, and did you notice any cervical secretions yesterday? If you can answer no to both questions, then the likelihood that you'd become pregnant from unprotected intercourse is low. If you answer yes to either one of the questions, then you're in your fertile phase. Abstain from intercourse or use a backup form of birth control, such as a condom, on those days.

Use a chart or diary to write down your observations so that you can easily note changes and determine your fertile phase. For natural family planning to be effective, you must abstain from intercourse during this phase. Once the phase passes, your charting cycle begins again.

Yes. Natural family planning doesn't alter reproductive function, so it's possible to become pregnant immediately after stopping this form of birth control. In fact, because of your heightened awareness of your fertile phase — which you gained by following natural family planning methods — you may have an easier time predicting the time you're more likely to become pregnant if you decide to do so.

The effectiveness rate of natural family planning depends largely on your diligence in following your selected method and willingness to abstain from intercourse during your fertile phase. With perfect use, natural family planning can be highly effective. However, few couples use natural family planning methods perfectly, and therefore the methods may have slightly lower effectiveness rates.

Here's a look at the effectiveness rates of the different methods of natural family planning. Effectiveness rates are available for all methods except cervical position and dilation.

These effectiveness rates represent how effective each method is at preventing pregnancy for couples who use natural family planning for one year. For example, with typical use of the symptothermal method, 10 to 13 women out of 100 become pregnant. With perfect use, only two to three women out of 100 become pregnant.

There are no health risks associated with natural family planning.

Natural family planning provides no protection against sexually transmitted diseases (STDs), such as HIV/AIDS, genital herpes and gonorrhea.

Natural family planning is inexpensive. Some family planning clinics offer free training sessions on natural family planning techniques. Hospitals or other health centers may charge a minimal fee for such sessions.

Thermometers used to record basal body temperatures cost between $10 and $12 and are available at your local drugstore. The standard days method uses CycleBeads — at a cost of about $13 — to help you keep track of your fertile days.

Natural family planning is readily available. Although a prescription isn't necessary, formal training is a good idea to learn how to do it correctly. Many hospitals and family planning clinics conduct regular training sessions on natural family planning techniques.

As with any form of birth control, natural family planning has its advantages and disadvantages:

Using a fertility awareness method of birth control requires that you be diligent and responsible in charting your fertility patterns and avoiding intercourse on unsafe days. It's most effective when both partners are committed to making it work.