Human chorionic gonadotropin (hCG), a hormone primarily produced by the placenta, is tested in the blood and urine to detect pregnancy. The hCG blood test in pregnancy can detect pregnancy up to a week before your period. This is because hCG levels can be detected in blood as early as six days of embryo implantation. Peak hCG levels are attained in the first 14 to 16 weeks after your last menstrual period. After that, they start declining and become stable for the rest of the pregnancy (1). Read this post to know about the hCG blood test, when to go for it, how to detect the results, and the test’s accuracy.
What Is hCG Blood Test?
hCG blood tests help confirm pregnancy by checking the presence of the hCG hormone in blood. You can undergo these tests only at a clinic. The two types of hCG blood pregnancy tests that you might have to take include:
Qualitative hCG test: It checks for the presence of hCG in your blood and gives either a positive or negative result (2).
Quantitative hCG test: It measures the amount of hCG in your blood. It might help determine the exact age of the fetus or detect pregnancy complications, such as miscarriage or ectopic pregnancy—a complication in which the embryo implants outside the uterus (3). It also helps to monitor patients with molar pregnancies and GTD.
A quantitative hCG blood test is also referred to by other names, including:
Beta hCG blood test Repeat quantitative beta-hCG test Quantitative serial beta-hCG test Quantitative blood pregnancy test
How Soon Can A Quantitative hCG Test Detect Pregnancy?
An hCG blood test might detect your pregnancy as early as six to eight days after implantation of embryo (4). This means that it can detect pregnancy ten days to a week before your expected period date (5).
How Accurate is The hCG Blood Test For Pregnancy?
Blood tests are about 99% accurate. They may give false-positive or false-negative results in rare cases. A small sample of blood is enough to detect the presence and level of hCG hormone. Also, hCG blood tests are more reliable than hCG urine tests as they can detect even low levels of hCG and thus detect pregnancy much earlier (6). The factors that could affect the hCG blood test results could be (7):
Medications, especially fertility drugs and injections Presence of certain tumors (such as germ cell tumors), molar pregancy and GTD Multiple pregnancies like twins or triplets Recent pregnancy loss
Why Do You Need An hCG Blood Test?
An hCG blood test is usually done for the following reasons (2) (3) (7):
To determine pregnancy To know the fetal age To diagnose abnormal pregnancies such as molar pregnancy and ectopic pregnancy To detect a possible miscarriage As part of a screening test for Down syndrome To diagnose abnormal conditions (such as ovarian tumors) in non-pregnancy cases
What Are The Other Reasons For Performing Beta hCG Blood Test?
hCG is considered a tumor marker as it is present in some types of cancers. The conditions in which the hCG hormone is likely to be present include (9) (10).
Cancers of the ovaries and uterus Trophoblastic tumor Hydatidiform mole Testicular cancer (in the case of men)
hCG levels are found to be elevated in the case of cancers of the lungs, liver, stomach, and pancreas too.
How Is The b-hCG Test Performed?
The test is similar to any typical blood test. It requires a small amount of blood drawn from the vein in the arm (called venipuncture) and requires no special preparation. However, you should inform your doctor if you are taking any drugs, herbal preparations, nutritional supplements, or homeopathic medicines as they might affect the results. The test involves the following steps (8):
Does hCG Blood Test Pose Any Risks?
There may not be any major risks of an hCG test. The effects might be momentary. Some of them are (7) (11):
Pain or a stinging sensation at the puncture site Lightheadedness Bleeding under the skin (hematoma) Infection if the skin is broken
How To Read hCG Blood Test Results?
In a qualitative beta hCG test,
A positive result indicates that you are or were recently pregnant. A negative result indicates that you are not pregnant or test is taken too early (2).
In a quantitative beta hCG test, The result is given as a number (in milli-international units per milliliter – mIU/mL) that indicates the concentration of hCG hormone in the blood. The levels rise rapidly during the first trimester, and then decline and become steady over the rest of the pregnancy. The levels may vary depending on your gestational age. Your doctor can explain what the specific levels mean in your pregnancy. In a non-pregnant woman, the levels would be less than 3mIU/mL (12). Your healthcare provider will help you in interpreting the result. A higher hCG level than the normal range may mean any of the following (3):
Multiple pregnancies (such as twins or triplets) Uterine choriocarcinomas Hydatidiform mole or molar pregnancy Ovarian cancer
A lower hCG level than the normal range may mean any of the following (3):
Incomplete miscarriage Fetal death Ectopic pregnancy
hCG Blood Test Results: False Positives And False Negatives
It may be possible to get false results from an hCG test similar to urine or home pregnancy tests.
False-positive pregnancy test result: The test shows positive even though you are not pregnant. You may get a false-positive result if you are on any medications or injections (containing hCG) such as those used in fetility treatments or have certain cancers (7).
False-negative pregnancy test result: In this case, the test result shows negative, but you are pregnant. It may happen if the test is taken too early, before there is enough hCG produced in the blood. Medications or harmful habits such as smoking and drinking alcohol may also give a false-negative test result (13).
If the test shows negative, and if you think you are pregnant, the doctor might recommend the test again in a few days.
