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Human chorionic gonadotropin (hCG) is a hormone produced by the placenta during pregnancy to support and promote the development of the placenta and gonads in the fetus. It can be detected in blood tests 11 days after conception and in urine tests 1-3 days later. Normal hCG levels should double every 48 to 72 hours until the eighth and eleventh weeks, then stabilize. Doctors advise not to rely too heavily on hCG levels as they can vary widely, and ultrasounds are more accurate in diagnosing and predicting the viability of pregnancy. Low or falling hCG levels could signal a recent pregnancy, miscarriage, or ectopic pregnancy, while high levels could indicate a later pregnancy, molar pregnancy, multiple pregnancy, or ovarian cancer.
Human chorionic gonadotropin (hCG) is a glycoprotein hormone normally produced first by the cells that make up the placenta, then by the placenta during pregnancy. Its primary function is to support pregnancy by promoting the production of progesterone. This supports and promotes further development of the placenta in early pregnancy. This hormone causes progesterone to rise rapidly in early pregnancy, but slowly decrease as the placenta grows large enough to produce enough progesterone to sustain the pregnancy on its own. The glycoprotein also serves to promote the development of the gonads in the fetus and the production of androgens by the testicles of a male fetus.
Levels of hCG can first be detected about 11 days after conception, in a blood test. One to three days later, it can be detected with a urine test. Some highly sensitive tests can detect the hormone as early as a week after ovulation. Regular home pregnancy tests cannot detect hCG in the blood until at least 12 to 14 days after ovulation.
A typical pregnancy should have hCG levels that double every 48 to 72 hours until the eighth and eleventh weeks, at which time they begin to stabilize and remain constant throughout the pregnancy. This occurs in about 11% of pregnancies. As these levels get high, they will begin to double every 85 hours.
Pregnant women, especially those who have had fertility problems, place a lot of importance on hCG levels. Because of the wide range of what can be normal, doctors advise women not to take them too seriously. Some women have low growth hormone levels and still have a normal, healthy baby.
Blood levels of the hormone are measured in international milliunits per millimeter (mIU/ml). Anything less than 5 mIU/ml is negative in a pregnancy test, while anything above 25 mIU/ml is positive. Ultrasounds have been shown to be much more accurate in diagnosing and predicting the viability of pregnancy than hCG levels. Hormone levels can be tested in two ways: qualitative tests determine whether it exists in the blood or urine, while quantitative tests measure how much is in the bloodstream.
The gestational sac usually completes its formation once hCG levels reach 1,200 mIU/mL. If the hormone reading is low or falling, it could signal a more recent pregnancy than previously thought, a mother who has had or is experiencing a miscarriage or spoiled egg, or an ectopic pregnancy. Levels higher than those considered normal for the age of pregnancy may mean that the pregnancy is later than estimated, that a molar pregnancy is present, or that a multiple pregnancy or ovarian cancer exists.
After a miscarriage, hCG levels fall back to the prepregnancy range, which is below 5.0 mIU/mL, about four to six weeks later. In some fertility treatment regimens, women may receive injections of the hormone to encourage ovulation or to extend the luteal phase of the cycle. When the hormone is administered during pregnancy, its purpose is to stimulate progesterone to further support the pregnancy. The effectiveness of this practice, however, is currently controversial.
