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A quantitative pregnancy test is a test that checks levels of the hormone human chorionic gonadotropin (HCG), associated with pregnancy, in the blood or urine. Rather than simply confirming a pregnancy by registering the presence of this hormone, this test can be used to check on the health of a pregnancy. It may be used for women undergoing fertility treatment, women with failing pregnancies, and women who have recently experienced miscarriages. Results with a quantitative pregnancy test can take longer than a simple qualitative test checking for the presence of HCG but not measuring the quantity.
For this test, a doctor can use a urine or blood sample. Some clinics have their own labs and can check the sample right away, while in other cases, it may need to be sent out. The level of hormone in the sample is measured and compared with information about the pregnancy. Generally, this hormone starts appearing within 10 days after conception, and the levels rise at steady and very predictable rates.
If a woman tests positive for pregnancy but her HCG levels are not increasing as expected, it can mean there is a problem with the pregnancy. Failing pregnancies are associated with abnormal HCG levels that will show up on a quantitative pregnancy test, and likewise with ectopic pregnancies, where the pregnancy implants in the fallopian tube instead of the uterus. After women miscarry, their recovery can be monitored by checking on levels of this hormone with a quantitative pregnancy test. The levels should fall after the pregnancy loss.
Pregnancy tests like those used at home are qualitative; they look for the hormone and return a positive or negative result on the basis of whether the hormone is present. Quantitative tests provide more information about a pregnancy. They are usually more expensive to perform because more lab work is required, but can be important for assessing the health of a woman and the embryo she carries during pregnancy. If the results are abnormal, additional medical screening may be recommended to find out why.
Every pregnancy is slightly different, and sometimes HCG levels are off on a quantitative pregnancy test in a perfectly healthy pregnancy. Unusual results are a cause for further investigation and a possible repeat of the test, not panic. Women should be aware that doctors will usually avoid speculating on abnormal test results until they have an opportunity to learn more about them, as they do not want to worry their patients.