The Clearblue Advanced Digital Ovulation Test is the only one that typically identifies your 4 best days to get pregnant naturally - 2 more days than any other test. It identifies your 2 Peak Fertility days (Peak Fertility remains on the display continuously for 2 days) and, typically, 2 High Fertility days by accurately tracking 2 key fertility hormones, Luteinizing hormone (LH) and estrogen - plus your 2 typically High Fertility days before that. So you have more opportunities to get pregnant naturally.