The fertility awareness method (FAM) tracks your natural cycles of fertility to help prevent pregnancy. The rhythm method, which estimates the time of ovulation, is one part of FAM.

The fertility awareness method (FAM) is a natural family planning strategy that can be used to help prevent pregnancy. It involves tracking your natural cycles of fertility and ovulation.

FAM is among the least reliable methods of contraception. To increase its effectiveness, FAM combines the following methods of information collecting:

When using FAM, you need to abstain from sex during your most fertile days, a technique known as periodic abstinence. Alternatively, you can use backup contraception on your fertile days.

This article takes a closer look at the FAM method, including how it works and how effective it is.

You’re most likely to be fertile and get pregnant if you have contraception-free sex a few days before or during ovulation.

Ovulation happens when your ovaries release an egg. It occurs approximately once per month, about 12 to 16 days after menstruation. The specific day you ovulate depends on your cycle length. This is largely controlled by fluctuations in your sex hormone levels.

For some people, these fluctuations are quite consistent from one month to another. Others have more irregular menstrual cycles. A period occurs 11 to 14 days after ovulation if a pregnancy hasn’t occurred.

Once an egg is released from your ovaries, its life span is very short. Conception can occur only if the egg is fertilized 12 to 24 hours after the time of actual ovulation.

However, sperm can remain alive and viable in the body up to 5 days after ejaculation. So, it’s possible to have intercourse up to 5 days before you ovulate and get pregnant as a result.

These biological realities mean the actual period of viable fertility can last anywhere from 5 to 8 days. In general, you’re most fertile during the following times:

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

You’re less likely to get pregnant if you’ve accurately identified your fertile period and avoid contraception-free sex on those days each month.

Theoretically, this will prevent viable sperm from being present in your body at the same time as a viable egg. In turn, this will prevent fertilization and conception.

Menstrual cycles are unique to each person. To use FAM effectively, it’s important to pinpoint when you’re ovulating. There are several ways to track your ovulation cycle and fertility.

Using a combination of the following tracking methods improves the effectiveness of FAM pregnancy prevention:

  • Calendar rhythm method: In this method, you use past menstrual cycles to estimate the time of your ovulation. When used on its own, this is the least reliable method of birth control. It should be avoided if your menstrual cycles are shorter than 26 days or longer than 32 days.
  • Temperature method: Here, you track your basal body temperature (BBT) for several cycles by using a very sensitive basal thermometer to take your temperature before you get out of bed each morning. Due to hormonal surges, your BBT goes up 3 to 4 days after ovulation. BBT should not be used to predict ovulation in real time. It’s a retrospective tool to help someone determine whether or not they ovulated that cycle.
  • Cervical mucus method: In this method, you track the color, thickness, and texture of your cervical mucus to monitor your fertility. Your cervical mucus becomes thinner, slippery, and stretchy when you ovulate. Tracking your cervical mucus will require some practice.

Using all three of the above methods above makes FAM the most effective. You should also track at least 6 to 12 menstrual cycles before you begin to rely on FAM for contraception.

It’s best to talk with a doctor or take a course on fertility awareness before deciding whether FAM is right for you. Educate yourself about your body and its cycles.

FAM requires a significant and consistent investment of time and effort. But it can also be a great and effective choice for those who are willing to put in the time and develop their understanding of how it works.

The effectiveness of FAM depends on:

  • which fertility tracking methods you use
  • how regular your menstrual cycles are
  • how reliably you track your menstrual cycles
  • how long you abstain from sex around your ovulation date

FAM can be effective for couples who always use it consistently and correctly. That can be hard to do.

Among those who use FAM inconsistently or incorrectly, up to 24 out of 100 become pregnant each year, according to Planned Parenthood. That makes it one of the least reliable methods of nonabstinence-based birth control.

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FAM has several advantages. For example, it:

  • is inexpensive
  • is safe to use
  • requires no medication
  • produces no side effects
  • can be stopped easily and immediately if you decide you want to get pregnant

Practicing FAM can also help you and your partner learn about fertility. This may help you get pregnant later on if you so choose.

FAM doesn’t protect against sexually transmitted infections (STIs), such as chlamydia, herpes, or HIV. It also has a number of other disadvantages. For example:

  • You need to consistently track your menstrual cycles for at least 6 months before the method can be considered reliable.
  • You need to abstain from sex or use backup contraception during your fertile days.
  • Both members of the couple must be involved in the process.
  • FAM has a higher rate of pregnancy compared with many other forms of birth control, such as condoms, diaphragms, and birth control pills, patches, or injections. But if used correctly, it can be just as effective.

If you have irregular menstrual cycles, FAM may not be the right choice for you. Talk with a doctor or healthcare professional to learn more about birth control options and determine which one could work for you.