1 The heart's internal pacemaker regulates and times the beating of the heart via electrical signals.  Electrical signals start at the SA node, causing atria contraction, and then move on to AV node, delaying electrical impulses to allow blood from the atrium to fill the ventricles.
With the First Response new Early Response Twist Pregnancy Test, you can test as early as 6 days before your missed menstrual period. This is the only test that allows you to find out this early, as it is sensitive enough to capture the very scant amounts of the pregnancy hormone.
Many at-home pregnancy tests are sensitive enough to detect your pregnancy long before your missed period. However, the First Response at-home pregnancy test is the only one that can detect the hCG in your body at levels as low as 6.5 mIU/ml. It is also the only test that works six days early.