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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.
Fertility awareness is done to help a woman learn when she is likely to ovulate. This information can help a woman to:
To use fertility awareness as a birth control method:
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.
For fertility awareness to work well, it is best to use all of the following methods together.
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.
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.
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.
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.
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.
If you are using a home ovulation kit, follow the instructions on the kit exactly.
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:
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Fertility awareness methods will not work very well:
The calendar method will not work very well if:
The BBT method will not work well if you:
The cervical mucus method will not work very well if you:
The results of hormone monitoring may not be correct if you do not follow the home ovulation kit instructions exactly.
Anything that changes the results of one of the methods also changes the results of the combined method.
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.
Current as of:
February 11, 2020
Author: Healthwise StaffMedical Review: Sarah Marshall MD - Family MedicineAdam Husney MD - Family MedicineKathleen Romito MD - Family MedicineFemi Olatunbosun MB, FRCSC - Obstetrics and Gynecology
Current as of: February 11, 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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