The pregnancy tests on the market today range widely in their sensitivity in picking up the pregnancy hormone, hCG. In the chart below, the lower the number in the "hCG Detected" column, the earlier you can use the pregnancy tests. As a general rule, hCG levels, if you are pregnant, are between 5 - 50 mIU a week before your period is due. The hCG levels in your system should double every two to three days.
Please remember that every woman is different and the time it takes for the fertilized egg to implant in your uterus wall can vary. A common misconception is that implantion occurs 7 days after conception, but the research findings showed that first appearance of HCG (implantation) occurred 6-12 days after ovulation, with 84% of the pregnancies implanting on days 8-10 after ovulation. If you don't get a positive pregnancy test, it doesn't necessarily mean that you are not pregnant. It could be that you ovulated later than you thought (meaning that conception and subsequent hCG production didn't happen as when you expected) or that, for you, implantation took longer than the average. Your period arriving is a sign that you are not pregnant this cycle, as is a negative blood test from your doctor.
Is a super sensitive pregnancy test the best to use?
For most women, the resounding answer would be YES! It allows you to know earlier if your attempts to conceive were sucessful and get medical care as soon as possible. There *is* a down side to extra sensitive pregnancy tests though. 25% of all pregnancies unfortunately end in miscarriage and many of these being very early pregnancies. If you use a very sensitive pregnancy test, where you test before the day your period is due, you could catch an early pregnancy but end up going on to have your period anyway due to a very early miscarriage. Some women will find it very hard to deal with this sort of emotional rollercoaster.