Ovulation is the release of a single, mature egg from an ovary. This happens once monthly about two weeks after the beginning of menstruation in the average female. Once the egg is released, it travels down the fallopian tube where it may be fertilized by sperm within twenty-four hours of release.

A sudden surge in the level of Leutenizing Hormone (LH) causes ovulation. LH is always present in the body but in smaller amounts than are seen just prior to ovulation. Around the middle of the menstrual cycle, the pituitary gland releases more LH than any other time of the cycle. The LH surge can last from 1-3 days. The beginning of the LH surge precedes ovulation by 20-44 hours which is about one and a half days. The surge in LH can usually be detected in the urine 8-12 hours after it occurs in the serum.

There are currently two major methods used to determine when a particular woman is ovulating. Basal body temperature is one method. The basal body temperature (BBT) will fall abruptly one to two days prior to ovulation in most women. There is a basal body thermometer used to measure basal body temperature. The temperature of a healthy person when taken immediately upon awakening is considered to be the BBT. Basal conditions are defined as being found 12 hours after the following: a restful sleep, eating, with no exercise, and with no emotional excitement. Also, basal body temperatures should be taken in normal ambient temperature. In addition to the drop in BBT prior to ovulation, other symptoms of fertility are monitored. These symptoms include cervical mucus changes and general physical observations. Basal body temperature monitoring may be a useful approach initially for a couple attempting to conceive. It is an inexpensive option which also provides a woman with accurate data concerning her cycle length. This information is helpful when considering the purchase and use of in-home monoclonal antibody ovulation prediction kits.

The other method often used to determine time of ovulation is in-home ovulation prediction kits. These should be used after the woman knows the length of her cycle and a time frame when she can expect to ovulate which she can find by using the BBT method. In-home ovulation prediction kits help determine the woman's fertile period by detecting the increase in the concentration of LH in the woman's urine prior to and during ovulation. These kits were first marketed in the United States in 1985. These tests contain monoclonal antibodies specific for LH and use an ELISA or EMIT to elicit a color change proportional to the level of LH in the urine. A significant increase in the intensity of the color over baseline is indicative of the LH surge. Different ovulation prediction kits contain supplies for between 5 and 9 tests. Theoretically, the earlier testing begins in a cycle and the more consecutive days tested, the greater is the likelihood of predicting the day of ovulation.