A pregnancy test kit works by detecting HCG(Human Chorionic Gonadotrophin) a hormone produced by the placenta during pregnancy. Presence of HCG in urine or blood is an indication of pregnancy. It helps thicken a person’s uterine lining to support a growing embryo and sends a signal to the brain and? the body to stops menstruation. HCG levels rise after conception and continue to rise until about 10 weeks in pregnancy. Clear blue early digital kit detects pregnancy as early as 5 days before the periods is missed. It has a digital display that gives a countdown as the user waits for the results. It offers 3 minutes short waiting time!