Basal body temperature for natural family planning

Overview

Tracking basal body temperature may be helpful in predicting fertility. It helps people learn when their bodies might be able to get pregnant and when they might not. Keeping track of basal body temperature is a type of birth control called fertility awareness-based contraception. It also may be referred to as a form of natural family planning.

Basal body temperature is the body's temperature when it's fully at rest. When the body releases an egg from the ovaries, a process called ovulation, it may raise basal body temperature slightly.

In many people, fertility is highest during the 2 to 3 days before basal body temperature rises. By keeping track of your basal body temperature each day, over time you may be able to predict when you'll ovulate.

If you want to get pregnant, basal body temperature may help you know the best days to have sex to raise the likelihood of getting pregnant. If you don't want to get pregnant, using basal body temperature may help you know which days each month not to have sex or when to use another form of birth control.

Tracking basal body temperature alone may not be enough to keep from getting pregnant. Often, people use it along with other fertility awareness-based methods to help prevent pregnancy.

Why it's done

The basal body temperature method can help you know the best days to have sex to raise the likelihood of getting pregnant. Or it can help you know which days not to have sex or when to use another form of birth control if you're trying to avoid a pregnancy.

Tracking basal body temperature for either pregnancy or birth control is low cost, and it doesn't have any side effects. Some people may choose to track basal body temperature as a form of birth control for religious reasons.

Basal body temperature also may be used to help detect pregnancy. Following ovulation, a rise in basal body temperature that lasts for 18 or more days may be an early sign of pregnancy.

Tracking basal body temperature is often done along with tracking cervical mucus that comes out of the vagina, called cervical secretions, throughout a menstrual cycle. Some people also use an electronic fertility monitor to measure hormone levels in urine, which can help predict fertility. This combination of approaches is sometimes called the symptothermal or symptohormonal method.

Risks

Tracking basal body temperature to predict fertility for pregnancy doesn't pose any risks.

Using it for birth control doesn't pose any direct risks, either. But tracking basal body temperature doesn't offer any protection from sexually transmitted infections. And it's less effective than other forms of birth control. Research suggests that about 1 in 4 people using birth control methods based on fertility awareness gets pregnant after a year of typical use.

Tracking basal body temperature along with using another form of fertility awareness-based birth control may be more effective in preventing pregnancy than basal body temperature alone. This approach to birth control requires motivation and commitment. If you don't want to get pregnant, you need to avoid sex or use a barrier form of birth control, such as a condom, during fertile days every month.

How you prepare

To track basal body temperature, you need a digital oral thermometer or a thermometer designed to record basal body temperature. The thermometer should be accurate to two decimal places.

Before you begin tracking basal body temperature for birth control, it's a good idea to talk with your healthcare professional. Tracking basal body temperature might not be a good birth control choice if:

• You recently gave birth.
• You recently stopped taking birth control pills or other hormonal birth control.
• You recently had your first period.
• You're breastfeeding.
• You may be getting close to menopause.
• Your menstrual cycles are not regular.
• You have a medical condition that could interfere with ovulation, such as polycystic ovary syndrome.

Factors other than ovulation that may cause basal body temperature to go up or down include:

• Illness.
• Infections.
• Fever.
• Some medicines.
• Certain gynecologic conditions.

What you can expect

To track basal body temperature:

• Take your basal body temperature every morning before getting out of bed. Use a digital oral thermometer or one that's made to measure basal body temperature.

  For the most accurate results, take your temperature the same way every day. Also, try to take it at the same time each day, when you first wake up.

• Track your temperature readings. Record your daily basal body temperature and look for a pattern over time. You can do this on a paper chart or with an app designed for this purpose.

  Basal body temperature may go up slightly during ovulation. It's typically less than a 1/2 degree F (0.3 C). Ovulation has likely happened when the slightly higher temperature stays steady for three days or more.

• Plan sex carefully during fertile days. Fertility typically is highest about two days before basal body temperature rises. But sperm can live up to five days in the reproductive tract, so pregnancy may happen throughout that time.

  If you don't want to get pregnant, don't have sex from the start of your period until 3 to 4 days after basal body temperature rises. Or if you have sex during that time, use a barrier form of birth control, such as a condom.

  If you want to get pregnant, the best time to have sex typically is 2 to 3 days before ovulation.

Many apps are available to track menstrual cycles. Some apps, such as Natural Cycles and Clue, may be useful for identifying days during a cycle when you're more likely to be fertile. That information is based on details you put into the app about your menstrual cycle. If you're interested in using this type of app, talk with your healthcare professional first about the risks and benefits.