What a hCG Blood Test Is:
Human chorionic gonadotropin, or hCG, is a hormone produced in the body during pregnancy. An hCG blood test measures the level of hCG detectable in the blood. The tests can be qualitative (returning a yes/no answer of whether the woman has hCG in her blood) or quantitative hCG tests (returning a measurement of the amount of hCG in the blood).
Why Doctors Order hCG Blood Tests:
Some doctors test hCG levels in early pregnancy as a routine part of prenatal care for all women. Others use urine-based hCG tests to confirm pregnancy and order blood tests only when they need more information about what is going on in a particular patient’s pregnancy, such as for a woman having vaginal bleeding in pregnancy or other miscarriage symptoms.
Doctors may want to see whether or not the hCG is in a normal range for a specific point in pregnancy, or they may want to look at hCG doubling times in two blood tests over a period of days to get an idea of whether the pregnancy is progressing as it should be.
How to Prepare for an hCG Blood Test:
An hCG blood test does not require any special preparation or planning, and you do not have to fast before having your blood drawn. The results should not be affected by the time of day you get your blood drawn or the amount of water you drink before the test.
Having Serial hCG Blood Tests:
Serial hCG blood tests are two quantitative hCG blood tests done two to three days apart. In early pregnancy, the hCG level is supposed to double roughly every two to three days. If the hCG doubling time is slower or if the level decreases over time, this is a possible sign of miscarriage or ectopic pregnancy.
If you are having hCG levels checked because of miscarriage symptoms in early pregnancy, your doctor will most likely need you to have serial blood tests rather than a single hCG level in order to get information on how your pregnancy is progressing.
What the Results Mean:
Your doctor is the best person to tell you what your hCG levels mean, because normal hCG levels vary heavily from person to person, and single hCG levels (even single low hCG levels) do not give much information on how a pregnancy is progressing.
Your doctor can compare the information from your hCG results to other information in your medical history, such as whether or not you are having miscarriage symptoms, in order to make a diagnosis.
In general, however, if the hCG levels are dropping in the first trimester, this probably a sign of impending miscarriage. Slow-rising hCG levels that do not double every two or three days in early pregnancy can be a sign of problems but can also still result in a normal pregnancy.