From Dawn Stacey M.Ed, LMHC,
Your Guide to Contraception.
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About.com Health's Disease and Condition content is reviewed by Meredith Shur, MD

Pregnancy tests can be either performed at home or in a doctor's office. A pregnancy test can determine if an unintended pregnancy has occurred. Both types of pregnancy tests examine whether the "pregnancy hormone," human chorionic gonadotropin (hCG), is present. A woman's body only releases hCG when she is pregnant.

HCG is produced once a fertilized egg implants in the uterus. In most women, this occurs about 6 days after conception. The hCG levels increase significantly with each passing day.

Studies indicate that most pregnancy tests will provide accurate results if a woman waits one week after a missed period to take a test.

Home Pregnancy Tests

There are many different types and brands of home pregnancy tests. They all function in the same manner -- they check a woman's urine for the presence of hcG. Results for urine tests are immediate than those for blood tests.

Most grocery stores and drugstores sell home pregnancy tests. Depending on the brand and how many tests come in the box, the cost is between $8 and $20. Many home pregnancy tests maintain that the test can tell if you are pregnant on the day you expect your period. Research indicates that most home pregnancy tests do not consistently detect pregnancy that early. If they do, the results are often very faint.

• More Information On: Home Pregnancy Tests

Blood Pregnancy Tests

Blood tests can detect hCG earlier in a pregnancy than urine tests. They can confirm a pregnancy about 6 to 8 days after you ovulate. However, the results of a blood pregnancy can take a few days to receive.

Doctors use two types of blood pregnancy tests.

• A quantitative blood test (or the beta hCG test) assesses the exact amount of hCG in the blood. Because it can detect even trace amounts of hCG, it is a very accurate test.
  
  
• Qualitative hCG blood tests only confirm whether or not the pregnancy hormone is present. A woman will receive a yes or no answer, so the qualitative hCG blood test is about as accurate as a home urine test.

• More Information On: Blood Pregnancy Tests