Accufast One Step LH Ovulation Test 5'sOvulation is the release of an egg from your ovary. A low background level of Luteinizing Hormone (LH) is always present in your urine. At about the middle of your monthly cycle, the LH increases suddenly to a high surge level which causes the release of an egg from your ovary (ovulation) about 14 to 48 hours later. To become pregnant, the egg must be fertilized with a sperm cell in time. Therefore, your most fertile time is when you are ovulating.