Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Quantitative HCG measurements can allow precise prediction of the age of the fetus. It is also used when an abnormal condition that can elevate HCG level is suspected.

A pregnancy test is usually based on detection of HCG, which is secreted by the fertilized egg. HCG appears in the blood and urine of pregnant women as early as 10 days after conception.

HCG maintains progesterone production by the corpus luteum in the early part of pregnancy. By the time HCG levels drop at the beginning of the second trimester, the placenta can make sufficient progesterone to maintain the uterine lining (endometrium). However, HCG may also be elevated in abnormal circumstances in men as well as women.

• choriocarcinoma of the uterus
• hydatidiform mole of the uterus
• normal pregnancy
• ovarian cancer
• testicular cancer

• fetal death
• incomplete miscarriage
• threatened spontaneous abortion
• ectopic pregnancy

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins