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Fertility Awareness

Test Overview

Fertility awareness is a way to check the changes your body goes through during your menstrual cycle. (It's 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's possible to become pregnant if you have sex 5 days before you ovulate.

For fertility awareness to be used as birth control, either you must not have sex or you must use another method of birth control for 8 to 16 days of every menstrual cycle. Other 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 most effective way 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. They include the calendar (rhythm) method, the basal body temperature (BBT) method, and the cervical mucus method (Billings method).

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 can avoid intercourse or use another method of birth control around the time of ovulation.

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's 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 isn't the best choice for women who have short, long, or irregular menstrual cycles.

Standard days method (SDM)

On the first day of your period, move the ring to the day 1 bead 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. The days when you are likely to become pregnant or not likely to become pregnant will have different colored beads to help you track. This method works best for women who have cycles between 26 and 32 days long.

There are also computer and smartphone apps you can use to track your cycle.

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 or Celsius temperatures 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.

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 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.

Credits

Current as of: October 8, 2020

Author: Healthwise Staff
Medical Review:
Sarah Marshall MD - Family Medicine
Adam Husney MD - Family Medicine
Kathleen Romito MD - Family Medicine
Femi Olatunbosun MB, FRCSC - Obstetrics and Gynecology

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