Most Women do not realize that pregnancy tests look for a special hormone in the urine or blood that is only there when a woman is pregnant. This hormone, human chorionic gonadotropin (hCG), can also be called the pregnancy hormone.

The pregnancy hormone, hCG, is made in your body when a fertilized egg implants in the uterus. This usually happens about 6 days after conception. But studies show that the embryo doesn't implant until later in some women. The amount of hCG increases drastically with each passing day you are pregnant.

Many home pregnancy tests claim they can tell if you're pregnant on the day you expect your period. But a recent study shows that most don't give accurate results this early in pregnancy. Waiting one week after a missed period will usually give a more accurate answer.

There are basically two types of tests. Blood tests and urine tests. Both tests check for the hGC hormone. Many women prefer the urine test bacause it can be preformed at home but to get the most accurate results a blood test is required.

Do not be afraid of the home pregnancy tests, many claim to be 99% accurate on the day you miss your period. But research suggests that most HPTs do not consistently spot pregnancy that early. And when they do, the results are often so faint they are misunderstood. If you can wait one week after your missed period, most home pregnancy tests will give you an accurate answer. Ask your doctor for a more sensitive test if you need to know earlier.

When a home pregnancy test will give an accurate result depends on many things. These include:

How long it takes for the fertilized egg to implant in the uterus after ovulation. Pregnancy tests look for the hormone human chorionic gonadotropin (hCG) that is only produced once the fertilized egg has implanted in the uterine wall. In most cases, this happens about 6 days after conception. But studies show that in up to 10 percent of women, the embryo doesn't implant until much later, after the first day of the missed period. So, home pregnancy tests will be accurate as soon as one day after a missed period for some women but not for others. How you use them - Be sure to follow the directions and check the expiration date. When you use them - The amount of hCG in a pregnant woman's urine increases with time. So, the earlier after a missed period you take a HPT, the harder it is to spot the hCG. If you wait one week after a missed period to test, you are more apt to have an accurate result. Also, testing your urine first thing in the morning may boost the accuracy. Who uses them - The amount of hCG in the urine at different points in early pregnancy is different for every woman. So, some women will have accurate results on the day of the missed period while others will need to wait longer. The brand of test - Some home pregnancy tests are more sensitive than others. So, some tests are better than others at spotting hCG early on. Keep in mind that many over-the-counter medications can effect the outcome of any pregnancy test.