HCG, or human chorionic gonadotropin, is a hormone that helps to maintain pregnancy. Because hCG is the mechanism through which a fertilized egg or embryo communicates to your body that you're pregnant, hCG levels are important to a healthy pregnancy. There are several reasons that you might have a high hCG.
HCG Function
The purpose of hCG is to communicate to your body that you're pregnant. HCG, secreted by tissue in a developing embryo, maintains the corpus luteum, which is specialized hormone-secreting tissue in your ovary. Without hCG, the corpus luteum disintegrates, and your progesterone and estrogen levels fall. This results in sloughing of the uterine lining, or a menstrual period. To maintain your uterine lining -- and therefore your pregnancy -- you must have proper blood levels of hCG.
HCG Levels
Typically, hCG starts building up in your bloodstream in the third week of pregnancy, which is the first week after conception. According to the internet site AmericanPregnancy.org, hCG levels vary greatly. For instance, three weeks after your last period -- or one week after conception -- your hCG should be anywhere between 5 and 50 mIU/mL. While pregnancy tests can detect hCG in the urine, they can't tell you what your hCG level is -- only a blood test at the doctor's office provides quantitative information.
High HCG
In general, high hCG isn't a bad thing -- if you're on the high end of the normal range for hCG levels in a given week, you're likely experiencing a completely normal pregnancy. One downside to high hCG is that some of the symptoms of early pregnancy are due to hCG, and can be exacerbated in women with high hormone levels. In their book "What To Expect When You're Expecting," Heidi Murkoff and Sharon Mazel note in particular that women with high hCG may have more morning sickness.
Potential
If you have very high hCG levels -- that is to say, if you're well above the high end of the normal range for a given week -- the two most likely possibilities are that you're having a multiple pregnancy or that you're further along than you think, explains AmericanPregnancy.org. Twins and higher order multiples increase hCG levels significantly. Because hCG levels double every 48-72 hours, if you're not having twins but have high hCG, it's also possible that you conceived earlier than you think you did.
Molar Pregnancy
One further possibility, notes AmericanPregnancy.org, though rare, is that you could be having a molar pregnancy if your hCG levels are very high. Molar pregnancies act like pregnancies, but don't generally include development of an embryo. They're the result of genetic abnormalities that lead to proliferation of hCG-secreting tissue, hence the high hormone levels, but don't lead to development of the cells that have potential to become a baby. Your doctor can do an ultrasound at around six weeks to look for a heartbeat, which rules out the possibility of a molar pregnancy.
References
- "What to Expect When You're Expecting"; Heidi Murkoff and Sharon Mazel; 2008
- AmericanPregnancy.org: hCG Levels
