A pregnancy test can either use a woman's urine or her blood to determine if a baby has been conceived. What the pregnancy test does is look for a hormone called chorionic gonadotropin (hCG) that is only present in a woman's body when she is pregnant.

This hormone is created when the egg is fertilized and then implanted in the uterus. The approximate timing is six days after the woman has conceived, although some women's eggs don't implant until considerably later. hCG increases dramatically each successive day in the pregnancy.

Most home pregnancy tests can't be counted on for accuracy until one week after a missed menstrual period. The home test will study your urine, while only a physician can do a pregnancy blood test.

Most women use a home pregnancy test, and then follow up with their physician for confirmation and pre-natal care. This first obstetric visit also includes a pelvic exam.

A blood test can confirm pregnancy much earlier than a urine test can do so - generally about 6-8 days after the woman ovulates. This is the time when the egg is released from the woman's ovary. There are two types of blood tests - quantitative and qualitative. While the quantitative blood test is the most accurate, measuring the amount of hCG in the blood and therefore how far along the pregnancy is, the qualitative blood test simply verifies hCG is present in the blood. The latter, therefore, is no more accurate than the urine pregnancy test, except it can verify pregnancy earlier.

It is very easy to obtain and then take a home pregnancy test, and you only need to spend up to $20 at your closest pharmacy or super center. Most home tests require that you hold a stick in your stream of urine; while some have you collect your urine in a container and then dip the stick into it. It is recommended, for accuracy, that you use the test when you first wake in the morning.

You only need to wait a very few minutes for the results. Depending on the brand you'll look for a line or a certain color to determine if your test is positive or negative. Most home pregnancy test vendors suggest that you repeat the test again in a few days to confirm the results, especially if the results are negative.

Home pregnancy tests are highly accurate if done correctly. To assure accuracy you must follow the test's directions and make sure the expiration date has not passed. You should not rely on a home test that is taken within the first week of a missed period. Women's hCG hormone levels vary and some can show high amounts within days of implantation while others must wait another week before it's obviously there.

Of course, like anything else, the quality of the product and its accuracy can vary from brand to brand.