When the moment comes, you depend on pregnancy test accuracy. The most sensitive at-home pregnancy tests should be able to detect pregnancy before the first day of your expected period and should be able to identify more than one form of the pregnancy hormone hCG. For example, they should be able to detect not only hCG but also a variant of the pregnancy hormone, hyperglycosylated hCG or hCG-H.
The cell, that originates when a fertilized egg is implanted in the uterine wall, initially secretes the pregnancy hormone variant hCG-H. This hormone variant is actually produced in the earliest stages of pregnancy before the primary pregnancy hormone, hCG, which is produced immediately following implantation by a different set of cells.
FIRST RESPONSE™ pregnancy test accuracy is unsurpassed. Enhanced technology detects lower levels of hCG. The more sensitive a pregnancy test is, the earlier you will know if you are pregnant. In fact, the FIRST RESPONSE™ Early Result Pregnancy Test can detect the pregnancy hormone earlier than any other at-home pregnancy test so you can get an early start on making healthy choices for both you and your baby.
It is important to note that some women may not have detectable amounts of pregnancy hormone in their urine until after the expected period. This is because hCG levels vary between women, and because some women sometimes have difficulty predicting the exact date of their next period
1 Women’s Health Journal November ’09 Publication: Embryonic Development and Pregnancy Test Sensitivity