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.
For its high sensitivity, accuracy, and speedy results, a First Response manual pregnancy test is the one youâll want to get. Itâs the most sensitive over-the-counter pregnancy test you can buy. It also is more likely to tell you âyesâ when youâre actually pregnant, and can do it in as little as 30 seconds.