The Clearblue Pregnancy Test with Weeks Indicator is the first and only test that is as accurate as an ultrasound scan at dating pregnancy*. Its smart dual sensor not only tells you in words on the digital display if you're pregnant or not pregnant, it also tells you how far along you are – the weeks since conception are shown as 1-2, 2-3 or 3+. You can test 5 days before your missed period (which is 4 days before your expected period). In lab testing, 98% of pregnant results were detected the day before the expected period, 97% 2 days before the expected period, 90% 3 days before and 65% 4 days before the expected period. (*Weeks result 97% in agreement with later ultrasound dating scan. Based on studies of 187 women comparing result to ultrasound dating).