The LH (Luteinizing Hormone) which is in the urine of normal women will increase dramatically in the middle of the menstrual cycle. The LH increase, triggers ovulation, which is when the egg is released periodically from normal fertile women. The World Health Organization (W.H.O.) experts state that LH testing is a reliable way to detect ovulation. Ovulation will occur after 24-48 hours following a positive test.