HCG is a short name for the hormone called human chorionic gonadotropin. This hormone isn't made or secreted by adults--male or female. Instead, it comes from specialized tissue in a fertilized egg and developing embryo. The job of hCG is to help maintain a pregnancy, and hCG testing can provide a physician or pregnant woman with some information.
HCG Function
The role of hCG is to help your body to recognize that you've conceived. After you ovulate, tissue in the ovary called the corpus luteum secretes hormones to cause the uterine lining to thicken. If no egg implants, the corpus luteum dies after about 14 days, and you menstruate. If fertilization occurs, the fertilized egg begins to secrete hCG, which communicates with the corpus luteum and keeps it alive--this in turn causes the uterine lining to remain in place.
HCG Secretion
Because hCG comes from a fertilized egg or developing embryo, it's not present in the bodies of non-pregnant women--unless they're taking certain fertility drugs. As such, physicians and home pregnancy tests rely upon hCG in the blood or urine of women as an indication of pregnancy. Home pregnancy tests can detect hCG in your urine several days before your missed period. Pregnancy tests in your doctor's office rely upon either blood or urine hCG to indicate pregnancy.
Test Types
At home, you can only test your urine for hCG. This kind of pregnancy test doesn't indicate your hCG level at all; it simply indicates whether hCG is present in threshold amounts. At the doctor's office, however, your physician can test your blood for hCG, explain Heidi Murkoff and Sharon Mazel in their book "What To Expect When You're Expecting." This test not only indicates whether hCG is present--meaning you're pregnant--but also quantifies the hCG.
HCG Quantities
Information about your hCG levels can help a physician to determine whether your pregnancy is progressing normally. For instance, your hCG levels should double every 48 to 72 hours. The American Pregnancy Association notes that typical pregnant women have quantifiable levels of hCG by three weeks after their last menstrual periods, with hCG levels peaking around nine to 12 weeks of gestation. After that point, hCG levels gradually fall through the remainder of pregnancy.
HCG Concerns
If your hCG levels don't double as expected, or are very low, your physician may begin to suspect a problem with your pregnancy. For instance, while low hCG isn't the only indicator of an ectopic pregnancy, many women with ectopic pregnancies have low hCG, according to the Advanced Fertility Center of Chicago. An ectopic pregnancy is a medical emergency in which the fertilized egg implants outside the uterus--they are not viable pregnancies, and must be terminated, or they could harm the mother.
References
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- American Pregnancy Association: Human Chorionic Gonadotropin (hCG): The Pregnancy Hormone
- Advanced Fertility Center of Chicago: Ectopic Pregnancy - Tubal Pregnancy
