Basal body temperature for natural family planning

The basal body temperature method — a fertility awareness-based method — is a type of natural family planning. Your basal body temperature is your temperature when you're fully at rest. Ovulation may cause a slight increase in basal body temperature.

You'll be most fertile during the two to three days before your temperature rises. By tracking your basal body temperature each day, you may be able to predict when you'll ovulate. In turn, this may help you determine when you're most likely to conceive.

If you're hoping to get pregnant, you can use the basal body temperature method to determine the best days to have sex. Similarly, if you're hoping to avoid pregnancy, you can use the basal body temperature method to help determine which days to avoid unprotected sex. Because the basal body temperature method alone doesn't provide enough warning time to effectively prevent pregnancy, it's generally used in combination with other fertility awareness-based methods if you're hoping to avoid pregnancy.


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Basal body temperature can be used as a way to predict fertility or as a part of a method of contraception, by helping you gauge the best days to have or avoid unprotected sex. Tracking your basal body temperature for either fertility or contraception is inexpensive and doesn't have any side effects. Some women may choose to use the basal body temperature method for religious reasons.

The basal body temperature method can also be used to detect pregnancy. Following ovulation, a rise in basal body temperature that lasts for 18 or more days may be an early indicator of pregnancy.

The basal body temperature method is often combined with another method of natural family planning, such as the cervical mucus method. This combination is sometimes referred to as the symptothermal method.

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