Clearblue Advanced Digital Ovulation Test 20 Tests is a product from Clearblue. By accurately tracking two key fertility hormones, estrogen and luteinising hormone, this test identifies two peak fertility days, as well as additional high fertility days before that. This means you have more opportunities to get pregnant. Unlike basal body temperature charting, ovulation predictor kits detect the rise in luteinising hormone that rises prior to ovulation to accurately detect the days before, and not after ovulation. This Clearblue ovulation test also detects estrogen, which rises prior to the LH surge to detect more fertile days. 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. Having intercourse on high and peak fertility days can maximise your chances of getting pregnant.