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Am Fam Physician. 2012;86(10):online

See related article on natural family planning.

What is natural family planning?

Natural family planning (NFP) is a way for couples to tell which days of the month the woman is most likely to get pregnant. They can then choose to have sex on those days if they want to have a child.

How does it work?

During each menstrual cycle, one of the ovaries releases an egg. This is called ovulation. A woman is most likely to get pregnant if she has sex just before or just after she ovulates.

There are a few ways to tell when a woman is about to ovulate. One is to check the fluid that comes out of her vagina. This fluid may be on her underwear, or on the toilet paper after urinating. Just before ovulation, the fluid is thin and stretchy to help sperm enter the uterus. It looks and feels like an uncooked egg white. On days when she is less likely to get pregnant, the fluid is thick and sticky.

Another way to tell when a woman is about to ovulate is by taking her temperature when she first wakes up in the morning. A special type of thermometer is used for this. It goes in her mouth and is called a basal (“BAY-zul”) thermometer. Write the temperature on a chart every day. Just before ovulation, the temperature will go up by about one-half of a degree.

Different types of NFP use one or both of these ways to track which days the woman is most likely to get pregnant. Another type also uses a test that measures hormones in the urine. One type of NFP can be used by breastfeeding women whose babies do not take any formula or solid foods at all. This method can only be used for the first six months after childbirth, and only by women who have not had a period since having their baby.

How well does NFP work for birth control?

Even if it is used correctly, NFP does not always work. In any given year, between one and five out of every 100 women who use NFP correctly will get pregnant. The risk of pregnancy is much higher if NFP is not used correctly or regularly.

Where can I get more information ?

Your doctor

AAFP's Patient Information Resource

Couple to Couple League

Creighton Model FertilityCare System

Family of the Americas Foundation

Marquette University

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