The concepts of natural family planning methods
Natural family planning (NFP) is the method that uses the body's natural physiological changes and symptoms to identify the fertile and infertile phases of the menstrual cycle. Such methods are also known as fertility-based awareness methods.
Once a month an egg is released from one of a woman's ovaries (ovulation); it can stay alive in the uterus for about 24 hours. Men can always produce sperm cells, and these can stay alive in the female reproductive system for about two to five days after being deposited in the vagina during sexual intercourse. What this means is that from a fertility point of view, women have periods of time during their cycle when they are unlikely to conceive, whereas men have no 'safe period'.
How is it possible to identify when the woman is in the 'safe period' (when pregnancy is not possible) and when she is in the 'unsafe period' (when she could get pregnant)?
There are physiological changes during the menstrual period that help to distinguish between the 'unsafe period' (when pregnancy is possible) and the 'safe period' (when pregnancy is not possible).
In what way can natural family planning methods prevent pregnancy?
Natural family planning methods prevent pregnancy by making it impossible for the egg and sperm to meet.
However, these methods depend on the awareness and ability of the couple to identify the fertile and infertile phase of each menstrual cycle, and also require cooperation between the couple to abstain from, or to have, sexual intercourse, depending on whether they are trying to avoid or achieve pregnancy.