Pregnancy test

  • Definition
    • 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.

  • How the Test is Performed
    • A pregnancy test is done using blood or urine. There are 2 types of blood tests:

      • Qualitative, which measures whether the HCG hormone is present
      • Quantitative, which measures how much HCG is present

      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 to 2 minutes for a result.

  • How the Test Will Feel
    • 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.

  • Why the Test is Performed
    • This test is done to:

      • Determine if you are pregnant
      • Diagnose abnormal conditions that can raise HCG levels
      • Watch the development of the pregnancy during the first 2 months (quantitative test only)
  • Normal Results
    • HCG level rises rapidly during the first trimester of pregnancy and then slightly declines.

  • What Abnormal Results Mean
    • 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 abnormal 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 provider will discuss the meaning of your HCG level with you.

  • Considerations
    • Urine pregnancy tests will only be positive when you have enough HCG in your blood. Most over-the-counter home pregnancy tests will not show that you are pregnant until your expected menstrual cycle is late. Testing before this will often give an inaccurate result. The HCG level is higher if your urine is more concentrated. 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 provider's office.

  • References
    • Warner EA, Herold AH. Interpreting laboratory tests. In: Rakel RE, ed. Textbook of Family Medicine. 8th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 15.

      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.