The Clearblue Advanced Digital Ovulation Test typically identifies 4 or more fertile days leading up to, and including the day of ovulation, at least twice as many as any other ovulation test.** The Clearblue Advanced Digital Ovulation Test is a breakthrough: it is the only ovulation test that not only detects the rise in luteinising hormone (LH), but also monitors the level of another key fertility hormone, estrogen, which increases in the days before the LH surge. Because your partner’s sperm can survive in your body for up to 5 days, you can actually become pregnant by having intercourse during the days leading up to ovulation.