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.
Most doctors recommend that you wait until the first day of your missed period before taking a home pregnancy test. A missed period is usually one of the first signs of pregnancy. This is usually around two weeks after conception. However, some tests are more sensitive than others and can be taken earlier.