Fertility Awareness

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Test Overview

Fertility awareness is a way to check the changes your body goes through during your menstrual cycle . (It is also called natural family planning or periodic abstinence.) Learning about these changes can help you know when you ovulate . You can then time sexual intercourse to try to become pregnant or to try to avoid pregnancy.

A woman is most often able to get pregnant for about 6 days each month. This includes 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, and 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 you have sex 2 to 3 days before you ovulate.

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 for 8 to 16 days of every menstrual cycle. Barrier methods include diaphragms and condoms. So 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 24 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 to find the time of ovulation. For fertility awareness to work best, you need to use all of these methods together. Check your body changes using these methods for several months before using them to avoid pregnancy.

Methods

  • Calendar (rhythm) method. For this 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. If you are regular, 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. She may be more likely to ovulate between 9 and 17 days before her next period. So the calendar method alone is not the best method of guessing when you might be ovulating.
  • Standard days method (SDM). This method works best for women who have cycles between 26 and 32 days long. Women who use this method usually use a special colored string of beads (CycleBeads) to keep track of their cycle.
  • 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 cause her BBT to fall 1 to 2 days before she ovulates. It will then rise a day or two after she ovulates. If you carefully measure and write down 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. If you watch, feel, and write down 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. It will be thick, cloudy, and sticky.
    • Just before and during ovulation, you will have more cervical mucus. It will be 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 to measure the hormone. You dip the stick or strip into your urine and read the level on the strip. Or you may 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. You also watch for signs of ovulation. (These include breast tenderness, belly pain, and mood changes.) The physical signs of ovulation help you learn when you ovulate.

Why It Is Done

Fertility awareness is done to help a woman learn when she is likely to ovulate. This information can help a woman to:

  • Become pregnant. Pregnancy is most likely to occur when sexual intercourse occurs close to the time of ovulation.
  • Avoid pregnancy. A couple may use fertility awareness for birth control if:
    • Their religious beliefs do not allow the use of other methods of birth control.
    • They wish to use a "natural" method of birth control that does not use medicines, surgery, or other devices.
    • They are willing to pay close attention to the woman's cycle.
    • They are willing to not have sex or to use another birth control method during fertile days.
    • Preventing a sexually transmitted infection (STI) is not a concern.

To use fertility awareness as a birth control method:

  • The woman should have regular menstrual cycles.
  • The woman must watch her body for changes during her menstrual cycle. She must keep good records of her cycles.
  • Both partners must do this method together. The couple must be willing to not have sex or to use a barrier contraceptive on days when the woman is fertile.
  • The couple must be willing to have an unplanned pregnancy if this is their only method of birth control.

How To Prepare

Before you use fertility awareness as a method of birth control, you need to find your pattern of ovulation. You can do this by keeping a record of three or four of your menstrual cycles. If you are trying to not become pregnant during this time, you can use a method of birth control that does not affect ovulation. (These include a condom, a diaphragm, and the copper intrauterine device [IUD]). Or you can choose to not have sex.

Basal body temperature is checked using a special oral thermometer marked in fractions of a degree. This allows you to see even small changes in temperature better than you can with a standard thermometer. Easy-to-read digital thermometers can be found in most drugstores or at family planning clinics. Do not use a digital ear thermometer for this method.

How It Is Done

For fertility awareness to work well, it is best to use all of the following methods together.

Calendar (rhythm) method

Write down 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 away (subtract) 18 from the number of days in your shortest menstrual cycle. Your first fertile day should be that many days after your menstrual bleeding starts. 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 starts. 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.

Sperm can live in your vagina 3 to 5 days after sex.

  • If you want to get pregnant, have sex every day or every other day from your first fertile day to your last fertile day.
  • If you do not want to get pregnant, do not have sex—or be sure to use another method of birth control—for 1 week before your first fertile day. In the example above, your fertile period is from day 8 to day 20, so protect yourself from becoming pregnant for these 12 days of your cycle.

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 advised for birth control. It must be used together with other birth control methods.

Standard days method (SDM)

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. This method works best for women who have cycles between 26 and 32 days long.

Basal body temperature (BBT) method

Take your temperature every morning for several months just after you wake up. Do it before you eat, drink, or do any other activity. Use a special ovulation thermometer or digital thermometer that shows tenths (0.1) of a degree. You can take your temperature orally or rectally. Be sure to use the same location and the same thermometer each time. Leave the thermometer in place for a full 5 minutes. Write down 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.

If you 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 you ovulate. 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 cycle.

Cervical mucus method (Billings method)

Each day, put one finger into your vagina and write down the amount and color of the mucus, and how thick or thin it is. 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. It will be thick, cloudy, and sticky. Just before and during ovulation, you will have more cervical mucus. It will be thin, clear, and stringy. It may stretch about 1 in. (2.5 cm) before it breaks.

If you want to get 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. Semen may be mixed with it.

If you do not want to get pregnant, do not have sex—or be sure to use another method of birth control—from the day your cervical mucus becomes clear and stringy 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 these two questions: Did I have secretions today? Did I have secretions yesterday? For all days that you answer "yes" to one of these questions, it is likely that you are fertile. You can get pregnant if you have unprotected sex. If you answer "no" to both questions on any day, you are not likely to get pregnant.

Hormone monitoring

If you are using a home ovulation kit, follow the instructions on the kit exactly.

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. You watch for signs of ovulation (such as breast tenderness, belly pain, and mood changes). You may have any of the following physical signs of ovulation:

  • Breast pain
  • An increase in sexual desire
  • Pain in your lower belly on one side or the other. This pain is called mittelschmerz. It can be sharp or dull and can last from a few minutes to a few hours. It occurs when the egg is released from the ovary on that side. The ovaries usually switch releasing an egg each cycle. The pain occurs on the side the egg is released from during that cycle.

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.

How It Feels

Keeping a record of your menstrual cycle (fertility awareness) takes time and effort every day. But it is important to keep a record to find out your most fertile time.

Risks

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. This includes the 5 days before ovulation.

Results

In most cases, your fertile days start 5 days before ovulation and end on the day of ovulation. Pregnancy can sometimes occur after ovulation, but it is less likely than in the days before ovulation.

Calendar (rhythm) method

If your menstrual cycle is 28 days long, you are most likely to ovulate about 14 to 15 days after menstrual bleeding starts.

If you do not want to get pregnant, the calendar method of birth control is not the best choice. This is especially true for women who have short, long, or irregular menstrual cycles. For this reason, the calendar method alone is never advised for birth control. It must be used together with other birth control methods.

Standard days method (SDM)

The SDM works best for women who have cycles between 26 and 32 days long. If you have more than one cycle a year that is shorter than 26 days or longer than 32 days, you need to use another method to avoid pregnancy.

Basal body temperature (BBT) method

Your basal body temperature (BBT) usually drops about 0.4°F (0.2°C) below your normal temperature 1 to 2 days before you ovulate. It then rises the same amount or more above your normal temperature 1 to 2 days after ovulation. It stays high until just before your menstrual period starts. Since the rise in BBT does not occur until after ovulation, you could get pregnant if you have sex just before or during ovulation.

Many women do not have a regular temperature pattern. This can make it hard to use this method to know when ovulation occurs.

Cervical mucus method (Billings method)

After your period, you will not have much cervical mucus. It will be thick, cloudy, and sticky. Just before and during ovulation, you will have more cervical mucus. It will be thin, clear, and stringy. It may stretch about 1 in. (2.5 cm) before it breaks.

For the 2-day method of checking your cervical secretions, ask yourself these two questions: Did I have secretions today? Did I have secretions yesterday? For all days that you answer "yes" to one of these questions, it is likely that you are fertile. You can get pregnant if you have unprotected sex. If you answer "no" to both questions on any day, you are not likely to get pregnant.

Hormone monitoring

Home ovulation tests measure the amount of luteinizing hormone (LH) in the urine. The results will be displayed on a test strip or a small computer unit.

Combined (symptothermal) method

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.

Fertility awareness works best when all the methods are used together. The number of unplanned pregnancies is 24 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 ovulation occurs.

What Affects the Test

For all methods

Fertility awareness methods will not work very well:

  • If they are not used consistently.
  • During stressful times.
  • When cycles are irregular.
  • After a baby is born, after you stop taking birth control pills, or just before menopause .
  • If both partners are not willing to work together to use them.

Calendar (rhythm) method

The calendar method will not work very well if:

  • You have irregular, short, or long menstrual cycles.
  • You breast-feed for more than 6 months.
  • You supplement breast-feeding with bottle-feeding.

Basal body temperature (BBT) method

The BBT method will not work well if you:

  • Have a fever.
  • Take some medicines, such as aspirin.
  • Are traveling, have problems sleeping, or have other stress.
  • Use a different thermometer or take the thermometer out too soon.
  • Take your temperature at a different time of day or take it in a different way.

Cervical mucus method (Billings method)

The cervical mucus method will not work very well if you:

  • Use vaginal lubricants or douche.
  • Are breast-feeding.
  • Have a vaginal infection.
  • Are close to menopause.

Hormone monitoring

The results of hormone monitoring may not be correct if you do not follow the home ovulation kit instructions exactly.

Combined (symptothermal) method

Anything that changes the results of one of the methods also changes the results of the combined method.

What To Think About

  • To use the fertility awareness methods at their best, think about taking classes on natural family planning from a trained health professional. Many women's clinics and hospitals offer classes.
  • Fertility awareness methods used for birth control do not protect against sexually transmitted infections (STIs) .
  • Home kits to help with fertility awareness are not always accurate. Different kits that measure luteinizing hormone (LH) may have different results. But they may help you when you use them with other methods. Kits for some of the other methods do not always predict ovulation correctly. More studies are being done.

If you are breast-feeding

  • Women who breast-feed after having a baby often go several months before they start having menstrual periods again. (They sometimes go longer than a year.) This is called lactational amenorrhea. For many women, full-time breast-feeding means you do not ovulate. So breast-feeding can be an effective method of birth control if all of the following conditions are met:
    • You gave birth less than 6 months ago.
    • You are breast-feeding only and do so day and night and your baby is not sucking often on a pacifier. Breast-feeding is not an effective method of birth control if your baby is also getting formula feedings.
    • You are not having menstrual periods.
  • Many women have a few days of bleeding about 6 or 8 weeks after they give birth. If you breast-feed full-time and don't use any formula, you may not get pregnant at this time. But if you start regular menstrual periods after this "6-week bleed," you should start using another method of birth control to prevent pregnancy.
  • Although breast-feeding may provide some protection against pregnancy, it is best to use another method while breast-feeding if you don't want to become pregnant.

References

Other Works Consulted

  • Fritz 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.
  • Trussell J, Guthrie KA (2011). Choosing a contraceptive: Efficacy, safety, and personal considerations. In RA Hatcher et al., eds., Contraceptive Technology, 20th ed., pp. 45–74. Atlanta: Ardent Media.

Credits

ByHealthwise Staff
Primary Medical Reviewer Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer Femi Olatunbosun, MB, FRCSC - Obstetrics and Gynecology

Current as ofFebruary 5, 2015