Ovulation is the process of final maturation of the egg (oocyte). At ovulation, the mature egg exits the ovary and enters the Fallopian tube. Conception occurs when that egg is fertilized by sperm in the middle of the Fallopian tube. Because the life span of the mature egg is limited to approximately 18 hours after ovulation, the arrival of the sperm must be precisely coordinated. In a normal human menstrual cycle, therefore, there are only 1-2 days in which conception is possible, since the sperm normally survives only up to 48 hours in the female reproductive system. It is therefore crucial to time the contact between sperm and egg to these 1-2 days.
Ovulation can be detected by several methods: ovulation predictor test, basal body temperature (BBT) chart, ultrasound, blood progesterone level, and endometrial biopsy. The first two methods are most commonly used.