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PATIENT INFORMATION

CLA: PREGNANCY TEST

PREGNANCY

Very soon after conception, the embryo begins to produce a chemical called hCG or human chorionic gonadotropin, which finds its way into the woman’s blood and urine. This hormone is critically important in keeping the pregnancy going and its presence allows the clinical laboratory to detect the pregnancy very early.  For many years, the pregnant woman’s urine was injected into any of several animals (rabbits, rats or frogs) and later, the animal’s ovaries checked for telltale signs of the hormone’s presence.

Today, the pregnancy screening test is based upon an antibody test to detect hCG in the urine. This test works well as a screening test, but does occasionally give a false negative (woman actually pregnant) or false positive (woman not actually pregnant) result.

The urine screening test for pregnancy is usually positive within two weeks after the last missed period, if the woman is truly pregnant. A much more sensitive test (indicates a positive pregnancy result earlier, if the woman is truly pregnant) is the hCG test using blood.  This is the test that is used to confirm a urine pregnancy test. The blood pregnancy test can measure the presence of hCG as soon as one week after conception.

TEST RESULTS

If your blood pregnancy test is positive, be sure and see a physician, to get an early start on a healthy pregnancy. If the result is negative and there is continued suspicion of pregnancy, the test should be repeated in 2 days, because in a normal pregnancy, the amount of hCG in the blood/urine doubles every 48 hours in the early weeks of pregnancy. 

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