The First Trimester

How do pregnancy tests work?

Pregnancy

All pregnancy tests look for a special hormone in the urine or blood that is only present when a woman is pregnant. This hormone, human chorionic gonadotropin (hCG), is also called the pregnancy hormone.

What's the difference between a urine and a blood pregnancy test? Is one better than the other?
There are two types of pregnancy tests - blood and urine tests. Both tests look for the presence of hCG, the pregnancy hormone. Today, many women use a urine test, or home pregnancy test (HPT), to find out if they are pregnant. HPTs do not cost a lot, are easy to use, can be done at home, and are private. When a woman has a positive result on an HPT, she needs to see her health care provider right away. The health care provider can confirm a positive HPT result with a blood test and a pelvic exam.

There are two types of blood tests you can get from a health care provider. A quantitative blood test (or the beta hCG test) measures the exact amount of hCG in the blood. This means it can pick up very small amounts of hCG, making it a very accurate test. A qualitative hCG blood test gives a simple yes or no answer to whether you are pregnant. This test is more like a urine test in terms of its accuracy.

Blood tests can pick up hCG earlier in a pregnancy than urine tests can. Blood tests can tell if you are pregnant about 6 to 8 days after you ovulate (or release an egg from an ovary). Urine tests can determine pregnancy about 2 weeks after ovulation. Some more sensitive urine tests can tell if you are pregnant as early as 6 days after you conceive, or one day after you miss a menstrual period.