If you test before your period is due and get a ‘Not Pregnant’ result, there is still a chance that you may be pregnant but that your hormone level is still not high enough for the test to detect. In clinical testing with early pregnancy samples the Clearblue gave the following results: 53% of women received a ‘Pregnant’ result 4 days early, 74% of women 3 days early, 84% of women two days early and 87% of women 1 day early.