Over 99% accurate at detecting pregnancy from the day your period is due. As accurate as a doctor`s urine test. Clearblue is the number one brand most recommended in a survey of 401 doctors (2012). Test up to 4 days early In lab testing, 98% of pregnant results were detected the day before the period was due, 97% were deteceted 2 days before the period was due, 88% were detected 3 days before the period was due & 56% were detected 4 days before. Weeks Indicator Weeks since conception shown as 1-2, 2-3, 3+ weeks on screen (93% accurate). Your doctor may date your pregnancy from the first day of your last period, not from when you conceived.