HCG is a hormone, produced by placental tissue. - Shortly after implantation of a fertilized ovum in the uterine lining, HCG begins to be produced.
- Levels of HCG approximately double every 2-3 days in a normal pregnancy.
- By the time of the first missed menstrual period, pregnancy tests are usually positive (with a sensitivity of 30-35 mIU/ml).
- Following a miscarriage, HCG levels initially fall quickly, then more gradually, until levels return to normal. This process takes, on average, about a month.
Urine is normally used for the test. A morning urine is more sensitive (in borderline situations) because it is more concentrated. Serum can be used, and is equally reliable. Elevations caused by: - Pregnancy
- Gestational Trophoblastic Disease
Decreases caused by: - Miscarriage (spontaneous or induced)
- Following obstetrical delivery
- With resolution of an ectopic pregnancy
| Normal Values: | mIU/ml | IU/L
| Non-pregnant | Negative | <24
| Pregnant | Positive | >25
|  Positive Pregnancy Test | Source: Operational Medicine 2001, Health Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau of Medicine and Surgery, Department of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300 |
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