How to use fertility awareness methods for natural birth control — and why they can be about as effective as the pill

birth control fertility period tracking — Fertility awareness includes the calendar method, where you track your period to determine when you are fertile.
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Fertility awareness methods of birth control allow you to naturally track fertility to understand when you can or cannot get pregnant.
For example, the calendar method tracks the length of your period, the cervical mucus method examines the color and texture of your cervical mucus, and the temperature method charts your basal body temperature.
You can learn how to use these methods effectively to achieve or prevent pregnancy, without hormonal birth control.
Visit Insider’s Health Reference library for more advice.

Birth control methods like the pill and hormonal IUDs are known to cause side effects like nausea, sore breasts, and spotting. As a result, some people have turned to natural methods of birth control, like the rhythm method.

The rhythm method was developed to help you track when you are fertile and most likely to get pregnant during your menstrual cycle. Nowadays, we have more modern fertility awareness methods that combine techniques like body temperature and cervical mucus to make a more accurate prediction.

These new methods can be effective at preventing pregnancy, but there is more work involved to track all of your body changes. Here’s how to use fertility awareness methods to track your menstrual cycle and determine when you can get pregnant.

How do fertility awareness-based methods work?

Fertility awareness-based methods (FABMs) can be used as natural birth control methods to increase or decrease your chances of getting pregnant.

“FABMs work by teaching couples to identify the short period of time when they may be fertile, and couples may then decide to have sex or not depending on whether they are trying to achieve or prevent pregnancy,” says Marguerite Duane, MD, a family medicine doctor for Modern Mobile Medicine and adjunct professor at Georgetown University.

There are about six days in your menstrual cycle in which you can get pregnant. About halfway through your menstrual cycle, your ovaries will release an egg which will move through your fallopian tubes for about 24 hours. Having sex on this day can get you pregnant, and because sperm can live in your uterus for up to six days, having sex in the few days before you ovulate can also result in pregnancy.

But periods can be irregular, so you will need more than just a calendar to determine when you are fertile. That's why FABMs also track physical signs of fertility, like your body temperature and the thickness of mucus in your vagina.

If you use FABMs correctly, they can be over 95% effective, just a bit less effective than hormonal birth control pills (which are 99% effective if used correctly). As with many types of birth control, however, people often don't use FABMs correctly, and effectiveness rates can plummet as low as 86%.

"To reduce this risk, it is important for people to learn to use the method correctly, typically via a trained instructor," Duane advises. You can find an instructor near you using the Association of Fertility Awareness Professionals website.

How to use fertility awareness-based methods

Most modern fertility awareness methods use multiple strategies to track your fertility, including the calendar, temperature, and cervical mucus methods.

How to use the calendar method

The calendar method is similar to the original rhythm method because it relies on tracking the length of your period and estimating when you will ovulate during your cycle. The calendar method uses the following steps:

Track your period for at least 6 months to get an average of how long your typical cycle lasts, starting from the first day of one period to the first day of the next period.
Take the number of days in your shortest cycle and subtract 18 from this number to find your first fertile day. For example, if your cycle lasts 28 days, you may start being fertile on day 10.
Take the number of days in your longest cycle and subtract 11 from this number to find your last fertile day. In a 28-day cycle, this would put your last fertile day as day 17.
To avoid getting pregnant, don't have sex or use another form of protection during your fertile days.
Keep tracking your period and updating your calculations as time passes.

By some estimates, the calendar method is about 95% effective when it is used perfectly, though it may not work as well for people with irregular periods. It will also work better if it's combined with other planning methods.

How to use the temperature method

The temperature method involves finding your basal body temperature – the lowest temperature your body reaches each day. Using the temperature method, you will need about three months of data on your basal body temperature before you begin. You will also need a thermometer that measures to at least one decimal place, as the changes in your temperature are very subtle.

Follow these steps for the temperature method:

To find your basal body temperature, you should take your temperature first thing when you wake up, before even getting out of bed or drinking water.
Take your temperature and record it every day – you will find that it changes throughout your cycle, caused by shifts in your hormones.
When you start ovulating, your temperature will rise about 0.5 degrees Fahrenheit and will stay higher for three days or more.
Once you finish ovulating, your temperature will drop again.
To avoid getting pregnant, avoid sex or use protection from two days before you ovulate to four days after ovulation.

How to use the cervical mucus method

The same hormones that trigger shifts in your body temperature also cause changes in the mucus on your cervix. This mucus, which comes out of your vagina as discharge, changes in color and texture throughout your menstrual cycle.

You can check what your cervical mucus looks like by putting clean fingers into your vagina and then looking at the texture and color of the mucus on your fingers. You can also use a piece of toilet paper or look at discharge in your underwear, but rubbing the mucus between your fingers is the best way to observe its texture.

To chart the changes in your mucus, you can write down your observations using descriptions like dry, wet, sticky, cloudy, and slippery. The cervical mucus method requires one month of checking your mucus to have enough information to know what your normal body changes look like. Your mucus generally follows this pattern:

After your period, you will have a few dry days without any mucus.
While your body is preparing to ovulate, you will produce yellow or white cloudy mucus that feels sticky to the touch.
Just before and during ovulation, you will have extra mucus that looks clear and feels slippery. This slippery mucus should last about four days.
After ovulation, your mucus may suddenly become cloudy and sticky again.
You will then have a few dry days before your period starts.

You are most fertile during the slippery days, so to prevent pregnancy, avoid sex or use protection while your mucus is slippery and for about three days afterward.

The limitations of fertility awareness methods

Combining all three methods together will give you the most accurate results, because each method has limitations:

The calendar method doesn't work as well for irregular periods and short cycles.
The temperature method can be inaccurate when you are stressed, drink alcohol, or have a fever.
The cervical mucus method doesn't work as well for people who are breastfeeding, have a sexually transmitted infection, or are early in menopause.

Collecting all of this information and combining the results can feel intimidating, but there are apps that can make the process easier. Many apps like Dot and Clue offer a calendar period tracker that can help you track your cycles.

Certain people may also need to take special precautions when using fertility awareness methods. For example, if you are breastfeeding, you should only use specially designed methods like the lactational amenorrhea method.

Insider's takeaway

Fertility awareness methods may work as well as birth control pills if you combine multiple methods and follow all instructions carefully. If you want to learn more about how to follow FABMs properly, talk to your doctor or look for an instructor who can help teach you more about each method.

"Anyone can learn to use a FABM and use it effectively if they are motivated to make their daily observations and if they have partner support," Duane says.