Human chorionic gonadotropin (hCG) is a hormone manufactured by the pituitary gland in non-pregnant women and by a growing fetus's placenta in pregnant women. Blood tests can be administered to learn the exact level of the hormone in the bloodstream.
Significance of hCG Levels
HCG can be assessed quantitatively or qualitatively. Quantitative hCG tests give an exact level of the hormone in the body. Qualitative tests tell you whether or not enough hCG is present to indicate pregnancy in a "yes or no" manner.
Function of hCG
In pregnant women, the embryo produces hCG to communicate to the ovaries that menstruation should not occur and that the corpus luteum, or empty egg sac, should continue to manufacture a hormone called progesterone until the fetal placenta can take over.
Types of hCG
According to the American Pregnancy Association, non-pregnant women of childbearing age have hCG levels less than 5 mIU/ml (milli-international units per milliliter). A level of 2 may not necessarily mean a woman isn't pregnant, but that she may have a pregnancy too early to be recognized clinically.
Dr. Tracy Gaudet in "Body, Soul, and Baby" states that in pregnant women hCG levels double approximately every 48 to 72 hours during the first six weeks of gestation. So, it may take two days for hCG levels to exceed 2 in a woman with an hCG level less than 2 who becomes pregnant.
An hCG level of 2 can multiply exponentially to 165,400 mIU/ml by the 24th week of pregnancy, per the APA's hCG guideline chart. For a woman who has recently miscarried, an hCG level of 2 means that the pregnancy has completely resolved itself and that menstruation may be approaching.