So if a couple wish to avoid a pregnancy, they know which days to avoid intercourse. No, natural family planning relies on the ability of a woman to be aware of signs of fertility regardless of the length or regularity of the cycle. Ovulation means the release of an egg from the ovary. It happens on one day only in each cycle. The life span of this egg is not more than 24 hours.
Conception takes place when the male sperm unites with the female egg.
If conception does not occur, the next period or menstrual bleed follows about 2 weeks after ovulation. A man is presumed to be fertile all the time. For woman the most useful indicators are cervical mucus, basal temperatures and cervix changes. Many woman also notice abdominal pain, blood-spotting and mood changes. It's a normal physiological event.