Advanced technology and clear digital results A woman can only get pregnant on a few days during her cycle. If she wants to get pregnant, these should be used. The Clearblue Digital Ovulation Test with Dual Hormone Indicator is the only test that can usually identify 4 fertile days in a cycle. This test measures 2 important fertility hormones to determine the days with increased fertility. This allows you to plan very precisely and have a better chance of getting pregnant. Thanks to the special algorithm, the test adjusts to your personal hormone profile. A Clearblue smiley appears on the digital display when your most fertile days have been identified. This is over 99%* reliable. Clearblue is the only brand with a reusable reader. If you have any ovulation test sticks left after detecting the first LH (luteinizing hormone) surge, you can use them in the next cycle with the same test holder to determine your fertile days, provided you are not already pregnant. *Simple urine tests have been shown to be more than 99% accurate in detecting the LH surge. They are 2x more accurate than calendar methods. In a UK study of 101 women, a simple calendar method was compared to the Clearblue Ovulation Test in terms of the likelihood of testing on the day of the LH surge (2011).