Testing for Ovulation

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.

• Ovulation Predictor Test: This test detects the surge of the hormone LH (luteinizing Hormone) in the urine or the rise of the hormone estrogen in saliva. The urinary test is more commonly used and more reliable of the two methods. Approximately 24-48 hours prior to ovulation, the hormone LH rises and falls over a 24-hour period. This is a signal for the egg to undergo final maturation, and also a means to predict when ovulation will occur (hence the name predictor test). Conception by natural means (intercourse) or artificial means (insemination) should be timed by the LH surge detector to the day of or the day after the LH test becomes positive.
• Basal Body Temperature (BBT) Chart: After ovulation, body temperature in normally ovulating women increases by one half to one degree Fahrenheit for two weeks. If pregnancy does not occur, the temperature drops to baseline at the time of menses. The basal body temperature remains elevated if pregnancy occurs. Measuring BBT allows one to retrospectively confirm ovulation. Intercourse or insemination should occur right before the temperature rise. The temperature must be taken immediately upon awakening, before any body movement, after at least two hours of sleep. The thermometer may be either a digital oral one or a special basal oral thermometer available in many drug stores.
• Ultrasound monitoring: After ovulation, the fluid-filled cavity (follicular cyst), which contained the egg, collapses. This collapse is a presumed evidence of ovulation and can be detected by serial daily ultrasounds. This method, however, is expensive and labor intensive. Ovulation may also occur even without follicular collapse. For these reasons, this method of ovulation detection is not routinely used.
• Progesterone Level: After ovulation, the hormone progesterone rises gradually until it reaches a peak 7-10 days later. High progesterone level, when performed 7-10 days after ovulation, confirms that ovulation has occurred and that progesterone production for that cycle is normal. Low progesterone level indicates either that ovulation has not occurred or that there is inadequate progesterone production (luteal phase deficiency).
• Endometrial Biopsy: The lining of the uterus changes predictably after ovulation. Testing a small sample of the lining (endometrial biopsy) may determine whether ovulation has occurred and whether progesterone production is adequate. The test involves sampling the interior of the uterus, normally with a thin plastic suction tube, 7-10 days after ovulation. Because the test is painful and expensive, and because a single blood level of progesterone may provide similar information, biopsies are infrequently performed for studying ovulation.