Fertility Based Awareness of FAB method is a natural family planning method. Some may choose this as they want to avoid the side-effects of certain contraceptives like the birth control pill, while others may use it’s for religious or cultural reasons. It takes a lot of practice to learn how to work with this method, and it is the least effective in pregnancy prevention. This method doesn’t use any devices or drugs as it combines the cervical mucus method, basal body temperature method and the calendar method.

How does Fertility Awareness Work?

The basal body temperature, the rhythm/calendar method and the cervical mucus method are combined to determine the most fertile period for a woman’s body. When a woman becomes aware of her fertile windows and her body’s ovulation, she can abstain from intercourse or use a barrier while having sex. 

The cervical mucus method helps predict when a woman is going to ovulate by tracking the vaginal discharge throughout the menstrual cycles. The calendar method also helps in predicting the fertile days by tracking the menstrual cycle’s length. The body temperature can be tracked during the menstrual cycle to find out a woman’s fertility period.

The FAB method requires a woman to be aware of her periods of fertility. She needs to track her menstrual cycle and chart her fertility pattern. The first day of menstrual flow is the start of the cycle and is known as Day 1. On Day 7 the egg gets ready to be fertilized by sperm.

Based on a 28-day cycle, Day 11 to 21 is the time for ovulation, when the egg is released from the ovary. This egg moves through the fallopian tubes to the uterus and must be fertilized within 12 to 24 hours. If sperms can fertilize this egg, then it attaches itself to the uterus lining and grows. But if there is zero fertilization, then the egg breaks up. On Day 28, if the egg isn’t fertilized, then the uterus sheds its lining, causing menstruation. This is the menstrual cycle and differs from woman to woman.

Trackable Indicators used in Fertility Awareness Methods

The following indicators used in the FAB method are based on certain facts, like a woman can get pregnant if she has unprotected heterosexual sex during the six days leading to ovulation, known as the fertile window and that women ovulate only once in one cycle. Sexual intercourse too far after or too far before ovulation will both not result in pregnancy, even if a couple has unprotected sex.

  • BBT

In this method, a woman can record and check her body temperature to track her fertile periods. A woman’s body temperature can rise 0.5 to 1 degree Fahrenheit or 0.3 to 0.6 degree Celsius at the beginning of the luteal phase or the 2nd half of the cycle after ovulation. Recording the basal body temperature tells a woman when she has already ovulated but not when she is going to ovulate. But tracking the BBT regularly every month can help a woman estimate when she ovulates.

  • Tracking cycles

Women can use an app or a calendar to track their menstrual cycles. Women can track their menstrual cycles for at least six periods, and they can determine when they ovulate.

  • Monitoring cervical mucus 

The cervical mucus or vaginal discharge changes through the menstrual cycle in response to progesterone and estrogen. It usually increases when a woman is ovulating or approaching ovulation. When mucus has an egg-white color, it suggests that either ovulation will occur soon or has happened a day earlier. A clumpy and thicker cervical mucus means a woman has ovulated.

LH urine tests can be used to track fertility. The luteinizing hormone goes up within 24 hours before ovulation, and it can be detected through urine tests that can be taken at home.

What are the Different FAB methods?

Some of the fertility awareness methods are explained in details as below:

Calendar Based Methods:

Calendar-based methods involve calculating fertile days on the basis of the prior month’s menstrual cycle. This method becomes functional only after charting at least three-cycle lengths. The first day of the period is known as Day 1. A cycle length is measured from Day 1 to the day before the start of the next period cycle. After going through 3 cycles, the woman can select the shortest and the longest cycle. This method needs frequent reassessments, particularly when cycle lengths vary a lot.

  1.  Calendar rhythm method – In this method, a woman needs to select the longest and shortest cycle lengths, then subtract ten from the longest cycle and subtract twenty-one from the shortest cycle. This will give her an idea of her fertile window in which she should avoid unprotected sex. For example, is a woman’s cycle lasts between 26 and 30 days, then the calculation must be 26-21 and 30-10. The result is 5-20 days which is her fertile period. If the period cycle is constant, for example, only 28 days, then her fertile window is between 7-18 days.
  2.  Standard days method – This simpler version of the calendar method mustn’t be used for a woman who has recorded two cycles outside the 26 to 32 days range in any year. Day 8 is considered the first fertile day and day 19 is considered the last one. Hence there shouldn’t be unprotected sex during days 8 to 19.

Calendar methods aren’t extremely reliable as five to forty-seven per cent of women fall pregnant every year, even after using this technique.

Symptom Based Methods:

Symptom Based method looks for signs of fertility to identify fertile windows.

  1.  Temperature Method – The basal body temperature method considers the lowest temperature taken in the morning. After ovulation, the increasing progesterone levels will raise body temperature by 0.2 to 0.5 degrees Celsius, indicating the end of ovulation. This temperature remains at the increased level until the next period. There are a few strict rules that need to be followed for measuring the temperature.
    • The temperature has to be taken at the same every day, either vaginally or orally, but it must be the same place through the cycle.
    • It must be taken immediately after waking up but before leaving the bed, before drinking, eating or performing any other activity.
    • The fertile window ends when a woman finds three consecutive days of temperatures that are much higher than the preceding six days. After this, she can have unprotected sex.
    • A digital thermometer is best for accuracy.
    • Body temperatures can rise due to factors such as alcohol, little sleep, illness, electric blankets, and sleeping later than usual.
    • This method may require multiple days of abstinence.

Cervical Mucus Method:

This method observes the variations in cervical mucus discharges and can identify fertile days as the mucus is affected by hormonal changes. Mucus has three distinct patterns:

  1. Infertile pattern post menstruation – this happens immediately after a period when the vaginal opening is dry or has a flaky, dense mucus with a sticky feeling to it.
  2. Fertile or ovulatory pattern – Increasing levels of estrogen can cause a feeling of wetness at the opening of the vagina. At this time, mucus is clear, watery and elastic just like raw egg white.
  3. Infertile pattern post ovulation – Increasing progesterone levels cause the mucus to be thicker, sticky and cloudy and can cause the vaginal opening to feel dry.

Any spotting or bleeding during the cycle must be treated as fertile days. Semen, menstrual blood and sexual excitement can mask the effects of fertile mucus, making mucus interpretation difficult.

Symptothermal Method:

In this method, a combination of 2 or more fertility signs like temperature, cervical mucus, changes in the cervix are considered to determine the fertile times. When methods are combined, the chances of correct prediction is increased.

Effectiveness of Fertility Awareness Methods

The effectiveness of Fertility Awareness Methods relies a lot on the level of motivation to avoid conception and the method used. They are 78% to 88% effective, meaning 12 to 24 women out of 100 using FAMs get pregnant annually. If couples use multiple FAB methods, then the chances of success are better.

If a woman is better at using the FAB methods using the right way, like tracking fertility signals, avoiding sex and using birth control on unsafe days, the more effective they are. But there is always a slim chance that a woman will get pregnant. Fertility awareness methods may not work, as well as other birth control methods. Implants and IUDs are known to be way more effective. Find more information on the use of IUD and their effectiveness

How Effective are FAMs as Contraceptives?

Most women do not use FAMs or other birth control options perfectly, and that is why the effectiveness of FAMs is lower. Different FAMs have different effectiveness rates, and there are very few studies that look into this. Many factors affect the effectiveness rates of FAMs such as menstrual cycles, research factors and the accuracy of measurements taken while observing FAM.

How Can You Make FAM’s More Effective

Like many birth control methods, FAMs can be effective when it is used perfectly. Its effectiveness also depends on both partners as they to support each to perform the steps correctly. Fertility awareness methods are highly effective when: 

  • The woman works with a doctor, nurse or counselor who knows how to use FAMs well.
  • You have the discipline and time to check for fertility signs and chart the cycle daily.
  • When the couple doesn’t mind avoiding penetrative vaginal sex or use another birth control during fertile days.

The best way to use FAMs is to combine multiple methods like calendar method, BBT method, and cervical mucus method. Each method relies on different signs to track fertile days and hence can increase the chances of effectiveness. All of them together can make tracking more accurate. For example, if you are stressed or sick, then your temperature chart will not be accurate. And under such circumstances, the cervical mucus method can keep you on track on charting.

Pros & Cons of Fertility Awareness Methods

Each method of birth control has its own advantages and disadvantages, and every woman chooses one which suits her best. Similarly, for fertility awareness methods, there are different pros and cons that one must consider.

Pros of Fertility Awareness Methods

  • There are no side effects.
  • It is quite effective when used consistently and in a correct manner.
  • It can be immediately reversed if a woman wants to have children.
  • This is a free or inexpensive method.
  • It does not contain synthetic hormone therapies like estrogen, which can cause an increase in heart risk.
  • There are no drugs or devices, and visits to the doctor’s office are not required.
  • It is effective for couples who want to try prevention of pregnancy naturally.
  • It is also beneficial for couples who have religious concerns over contraception.
  • Good for women who don’t have access to other birth control methods.

Cons of Fertility Awareness Methods

  • Requires diligence from the couple – both partners.
  • Needs accurate and consistent record maintenance.
  • Backup contraception or periods of abstinence are required for at least one-third of the month.
  • It is challenging for women who experience irregular menstrual cycles.


Fertility awareness methods are used by couples who want to get pregnant or those who want to avoid pregnancy. The goal of fertility awareness is to predict when ovulation will occur and when a woman is highly fertile. Couples who want to try for a child will have unprotected sex at this time, whereas those who don’t want children will avoid unprotected sex.

The fertile window’s length depends on how long sperm can survive in the uterus, which is usually five days and the life of an egg, which is usually 12 to 24 hours. Sexual intercourse too far before ovulation or too far away from the fertile period reduces the risk of pregnancy. But then again, FAM alone isn’t the most effective way to avoid pregnancy.

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