A pregnancy test measures a hormone in the body called human chorionic gonadotropin (HCG). HCG is a hormone produced during pregnancy. It appears in the blood and urine of pregnant women as early as 10 days after conception.
A pregnancy test is done using blood or urine. There are two types of blood tests:
The blood test is done by drawing a single tube of blood and sending it to a laboratory. You may wait anywhere from a few hours to more than a day to get the results.
The urine HCG test is usually performed by placing a drop of urine on a prepared chemical strip. It takes 1-2 minutes for a result.
For the urine test, you urinate into a cup.
For the blood test, the health care provider uses a needle and syringe to draw blood from your vein into a tube. Any discomfort you might feel from the blood draw will only last a few seconds.
This test is done to:
HCG level rises rapidly during the first trimester of pregnancy and then slightly declines.
HCG level should almost double every 48 hours in the beginning of a pregnancy. HCG level that does not rise appropriately may indicate a problem with your pregnancy. Problems related to an abnormally rising HCG level include miscarriage and ectopic (tubal) pregnancy.
An extremely high level of HCG may suggest a molar pregnancy or more than one fetus -- for example, twins.
Your health care provider will discuss the meaning of your HCG level with you.
Urine pregnancy tests will only be positive when you have enough HCG in your blood. If you are very early in your pregnancy, and the HCG level is below 25-50 mIU/mL, the test will be negative. The level is higher if your urine is more concentrated. So a good time to test is when you first get up in the morning.
If you think you are pregnant, repeat the pregnancy test at home or at your health care provider's office.
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Webster RA. Reproductive function and pregnancy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 25.