Birth Control: Rhythm Method (Fertility Awareness)

Written by the Healthline Editorial Team | Published on October 9, 2014
Medically Reviewed by Kenneth R. Hirsch, MD on October 9, 2014

What Is Fertility Awareness?

The fertility awareness method (FAM), previously called the rhythm method, is a way to prevent pregnancy by taking advantage of the natural cycle of fertility. It requires an understanding of the body’s natural ovulation cycle. The effectiveness of the various forms of fertility awareness methods varies.

Various forms of the fertility awareness based methods are more commonly known as:

  • natural family planning
  • fertility awareness method (FAM)
  • periodic abstinence

Women abstain from sex during their most fertile days. Instead of abstaining, some women use backup contraception on their fertile days.

How Does Fertility Awareness Work?

A woman is most likely to get pregnant or be fertile during and right before ovulation. Fertility, or being fertile, is the ability to conceive a child. Ovulation is when an egg is released from the ovaries. It occurs approximately once per month, about 12 to 16 days after menstruation. Once an egg is released from the ovary, its lifespan is actually very brief, with conception possible for only 24-48 hours after the time of actual ovulation. However, the male sperm can remain alive and viable in the woman’s body for up to five days after ejaculation. These biologic realities make the actual period of viable fertility anywhere from five to eight days in most cases, with substantial variations based upon particular characteristics of the partners, the frequency of ejaculatory intercourse during the fertile periods, and numerous other factors. The specific day on which ovulation occurs depends on your cycle length, which is largely controlled by regular, oftentimes fairly consistent (in a particular individual) fluctuations in the woman’s hormone levels.

Ideally, to use the fertility awareness method, you need to become clearly aware of your menstrual cycle and the biology occurring throughout it. You will want to keep records of at least six to 12 months of menstrual cycles and should use the full range of estimated fertility periods derived from both short and long cycles. According to UC Davis, when cycles range from 26 to 32 days, the fertile period is generally days 8 through 19.

As already mentioned, sperm can live for up to five days in a woman’s body. Therefore, a woman is most fertile:

  • five days before ovulation
  • the day of ovulation
  • within 12 to 24 hours after ovulation

Pregnancy is less likely if the fertile period has been accurately identified and unprotected sex is avoided on those particular days. Viable sperm should not be present at the same time as the viable, released egg. However, that being said, fertility awareness is amongst the least reliable modalities of contraception, with 20 or more pregnancies occurring annually per 100 women utilizing this method.

How Do I Track My Menstrual Cycle?

Every woman’s menstrual cycle is different. It’s important to pinpoint exactly when you are ovulating in order for this method to be effective. There are several ways to keep track of your fertility.

The three most common methods are:

  • the calendar method, which uses past menstrual cycles to estimate the time of ovulation. It is the least reliable fertility awareness method. Women whose cycles are shorter than 26 days or longer than 32 days should not use the calendar method.
  • the temperature method: Due to hormonal surges, a woman’s basal body temperature (BBT) goes up right after ovulation. By tracking your temperature first thing in the morning for several cycles, you can determine when in your cycle you ovulate. This requires using a very sensitive thermometer and taking your temperature before getting out of bed.
  • the cervical mucus method: Cervical mucus becomes thinner when a woman ovulates, in order to facilitate sperm access to the released egg. Tracking cervical mucus color, thickness, and texture can allow women to monitor their fertility. If you notice changes in mucus today or if you noticed them the previous day, you should refrain from unprotected intercourse.

The sympthothermal method is when all three methods are used together. Combining methods for fertility tracking makes them more effective. However, the fertility awareness method of contraception remains the least effective way to prevent pregnancy in persons who are sexually active. Women should track at least six to 12 cycles before they begin to rely on fertility awareness for contraception.

It’s best to talk to your doctor or take a course on fertility awareness before deciding if it’s right for you. Fertility awareness requires a significant and consistent investment of time and effort.

How Effective Is Fertility Awareness?

The effectiveness of an FAM depends on:

  • which fertility tracking method is used
  • how regular your cycles are
  • how reliably you track your cycles
  • how long you abstain from sex around your ovulation date

These methods can be successful for couples that always use them reliably and consistently. Nevertheless, the average failure rate for women using FAM is 18 or more percent annually, which leaves fertility awareness techniques among the least reliable methods of non-abstinence-based birth control.

What Are the Benefits of Fertility Awareness?

Fertility awareness has several advantages, including:

  • low cost
  • safety
  • no need for medical devices or medications
  • lack of side effects

In addition, using fertility awareness can educate a woman and her partner about fertility. This can help them to get pregnant later, if they so choose.

What Are the Disadvantages of Fertility Awareness?

This form of birth control does not protect against sexually transmitted infections. It also has a number of other disadvantages including:

  • the fact that both members of the couple must be involved in the process
  • the need to abstain from sex during your fertile days, or to use backup contraception
  • the need to consistently track your cycles for at least six months before the method can be considered reliable
  • a high failure rate compared with almost all other non-abstinence-based birth control methods (i.e. condoms, the pill, diaphragms, etc).

Fertility awareness is a poor choice for women with irregular menstrual cycles.

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