Effectiveness in Preventing Pregnancy
- Of 100 couples each year who use natural family planning methods up to 25 may become pregnant.
- Fertility awareness can be an effective type of birth control if more than one method is used, and if they are always used correctly. This may include use of condoms or other barrier methods during potentially fertile times of the menstrual cycle.
- A woman tracks signs such as the days of her menstrual cycle, her daily “at rest” temperature and/or changes in her cervical mucus over the course of each month so that she knows her fertile days and can abstain from sex or use birth control those days to avoid pregnancy.
- Fertility awareness methods can also be used to achieve pregnancy (get pregnant).
Office Visit Required
- No, but it’s a good idea to discuss fertility awareness methods with a health care provider. To search for a family planning center near you, use the clinic finder.
What is fertility awareness?
Fertility awareness-based methods help women and couples understand how to avoid pregnancy or how to become pregnant. A woman learns to recognize signs of her fertile days. She is most likely to become pregnant (conceive) during her fertile days.
A woman with a 28-day menstrual cycle has about 6 days a month when she can get pregnant. These include the five days before she ovulates (when an egg is released) and the day she ovulates. As most women have variable menstrual cycles, fertility awareness methods teach women and couples how to monitor the fertile phase. Predicting the fertile phase can be more difficult in women with variable length cycles.
Fertility awareness involves paying close attention to the menstrual cycle by using methods that include:
- Basal Body Temperature Method (BBT)
- Cervical Mucus Method
- Computation of Standard Days
When the BBT and cervical mucus methods are used together, it is known as the sympto-thermal method.
Basal Body Temperature Method
Basal body temperature is the “baseline” temperature when you first wake up in the morning. During ovulation—when the ovaries release an egg and you can get pregnant—the basal temperature goes up a little. You can predict the days you are likely to be fertile if you track and record your basal temperature each day for a few months
How it Works
Your basal temperature is typically between 96 and 98 degrees before you ovulate. After you ovulate, your temperature will rise just a bit, usually less than one degree. Such a small change is hard to detect and is best done with a basal body thermometer which is available at drug stores. Write down and keep track of your temperature each day. A Basal Body Temperature Chart can help you do that.
Knowing when your temperature increases will not tell you for sure when you are fertile, but it can give a pretty good idea. You are most likely to get pregnant two to three days before your temperature peaks and the day after that. After your temperature has been higher for three days, the chances of getting pregnant drop.
Keep in mind that sperm can survive in a woman’s body for up to a week after she has sex. And the best chance of pregnancy is if there are sperm present in a woman’s tubes when an egg is released. If you have sex without birth control up to a week before and for a day or two after you ovulate, you have the greatest chance of getting pregnant.
Cervical Mucus Method
With this method, you pay attention to the changes that happen with your cervical mucus (such as color and thickness) over the month.
How it Works
Just after your period ends, there a few “dry days” when no mucus is present. These are days when you aren’t likely to conceive (get pregnant).
As an egg gets ready to be released (known as ovulation), more mucus is produced and it’s often cloudy or whitish with a sticky feel. These are fertile days and couples wishing to avoid pregnancy should not have unprotected sex on those days.
The most mucus is produced just before ovulation. Here, it’s clear and slippery, like raw egg whites. It can be thick enough so it spreads apart on your fingers. This is the time a woman is most likely to get pregnant.
After three or four “slippery” days, less mucus is produced and anything you see is probably sticky and a darker “cloudy” color. This is usually followed by a few “dry” days before your period starts again. The time between the “slippery days’ and when your period starts are when pregnancy isn’t likely to happen.
Use a tissue or your fingers to check your mucus several times each day. Note whether it’s cloudy and tacky or clear and slippery. Chart the changes on a calendar. You can label days as Dry, Sticky/Cloudy, and Slippery/Clear.
Standard Days Method
With the standard days method, you predict fertile days by charting and recording how long your menstrual cycles last.
How it Works
Track how many days each of your menstrual cycles last. Use a calendar and write down when each cycle starts, beginning with the first day of your period. Keep a record of how many days your cycle lasts each month.
To get the best information, you’ll need to track and record how long your cycles last for at least six months to get a highly accurate charting of your menstrual cycle. If you can do this as long as 12 months, it’s even better.
To predict the first day you’re likely to be fertile—the most likely time for you to get pregnant if you have sex without birth control—in your new cycle:
- You will need your menstrual cycle information from at least the past six months, a calendar and a pen.
- Subtract 18 days from the total days of your shortest cycle. Take that number and count ahead from the very first day of your next period (count the day your period begins).
- Example: your shortest cycle lasted 27 days. 27-18= 9 days. On your calendar circle the date your next period starts, and beginning with that day count ahead 9 days. So if you period starts on the 2nd day of the month, you’d count ahead to the 10th day of the month. Put an “X” on the calendar for that day.
To predict the last day you’re likely to be fertile in the cycle:
- Subtract 11 days from the total days of your longest cycle. Take that number and count ahead from the very first day of your next period (count the day your period begins).
- Example: your longest cycle lasted 29 days. 29-11=18 days. On your calendar circle the date your next period begins, and starting with that day count ahead 18 days. If your period starts on the 2nd day of the month, you’d count ahead to the 19th day of the month. Put an “X” on the calendar for that day.
The days between the two “X’s” are when you’re most likely to get pregnant. If you don’t want to get pregnant, then don’t have sex on those days, or use birth control (like a condom, diaphragm, or cervical cap).
Keep this in mind: the standard days method can predict the days you are most likely to be fertile, but isn’t always 100% accurate, especially if your cycles don’t always last the same number of days. It’s best to use other fertility awareness methods, too.
Certain devices such as Cycle Beads can also help you track your cycle.
Drawbacks of natural family planning
- Your partner must agree and cooperate.
- Fertility awareness methods provide no protection against sexually transmitted infections (STIs) including HIV.
- Most women don’t have totally regular menstrual cycles or periods, so you cannot definitely know the exact days you can get pregnant.
- Fertility awareness takes time and effort each day to track days of menstrual cycle, chart temperature and/or cervical mucus.
- Viral infections that cause low-grade fevers can affect basal body temperature.
- Some medications such as antibiotics or antihistamines may change cervical mucus.
- If preventing pregnancy is a high priority, more effective methods of birth control should be chosen.
The American College of Obstetricians and Gynecologists
- Natural Family Planning FAQs Fact Sheet, accessed 6/5/13
Centers for Disease Control and Prevention
- Unintended Pregnancy Prevention: Contraception
- United States Medical Eligibility Criteria for Contraceptive Use, 2010
- US Selected Practice Recommendations for Contraceptive Use, 2013
Office on Women's Health
- Birth Control Methods Fact Sheet, accessed 6/5/13