Home pregnancy test accuracy can be close to 100% if the directions are followed correctly and if you test at the right time. Probably the number one issue with such tests is when they can be used. That is one of the most asked questions from women trying to conceive - "When to test for pregnancy? How early can I test?" The answer to this determines the accuracy of the test.

The answer to this question ultimately depends on 2 things.
1. When you ovulated.
2. IF conception occurred, when the fertilized egg implanted.

And the pregnancy test accuracy can also depend on what brand of pregnancy test you have and the sensitivity level. Most of the tests these days are fairly sensitive detecting the pregnancy hormone hcg levels in early pregnancy.

Here's an overview of what goes on in your body after ovulation:

Ovulation is when the ovary releases an egg into the fallopian tube. The egg will only live for 12 to 24 hours unless it's fertilized. For the best chance of fertilization there should be sperm already present in the fallopian tube. Sperm normally lives up to 72 hours but can live up to 5 days.

When the egg is fertilized by the sperm it will sit in the fallopian tube for several days - just dividing from a one-celled organism into a multi celled zygote. It will begin to float down and into the uterus. Once in the uterus the fertilized egg will find a spot in the rich thick lining to implant. It's not until this moment of implantation that the body will know it's pregnant. Before implantation takes place, the body does not know - the hormone pregnancy hCG has not been produced - and there can be no pregnancy symptoms.

Implantation can take place as early as 3 or 4 days post ovulation, but more than likely it takes place around 5 to 7 days past and as late as 10 days past ovulation. With this in mind you can see when you might obtain a positive pregnancy test. At the point of implantation the corpus luteum is messaged to maintain the uterine lining until the placenta is in place. hCG begins in production and can be detected in the blood and urine a day or so after implantation has taken place. Pregnancy implantation symptom is a bit of spotting - which may or may not be seen.

hCG doubles every other day - so at first the levels are low and even a sensitive pregnancy test may not pick it up. It's hCG that causes the first symptoms of pregnancy and you may experience symptoms a week or so before your period is due.

If the fertilized egg implants early you can possibly get a positive home pregnancy test result as early as 7 days post ovulation. It's more probable to get a positive on the test at 9 or later days. If it's a test that's not as sensitive, you may not see a positive until 12 to 14 days past ovulation.

The home pregnancy test accuracy ultimately depends on several things. Depends on what day past ovulation the fertilized egg implanted and depends on how sensitive your particular brand of home pregnancy test is. There's really no way of knowing when the egg implants other than the possibility of some vague pregnancy symptoms. It's possible to see a negative pregnancy test before seeing a positive. If you don't want to chance seeing a negative, wait until your period is late to test. In some women it could take 17 days or longer for a pregnancy test to register a positive result then your home pregnancy test accuracy will be greater.