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.
A pregnancy test with a sensitivity of 20 IU/L is more sensitive than one with 50 IU/L. A blood test administered by your doctor is more sensitive than the early home tests and can be taken between 7 and 12 days after you conceive. However, it is possible that these tests can be done too early and show a false negative result.