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What is a blood pregnancy test?

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Updated May 16, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Scientist examining blood sample in lab.
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Question: What is a blood pregnancy test?
I've taken a home pregnancy test and was told I should take a blood test. What is this and how is it different than a urine test?
Answer: A blood pregnancy tests will look for hCG in your blood. hCG, or human chorionic gonadotropin, is a hormone secreted in pregnancy and detectable by blood test about day 8 to 10 after conception. Whether you are taking a home pregnancy test that uses urine or a blood pregnancy test from your doctor or midwife, the results will be based on measurements of this hormone – be it in your urine or blood.

However, a blood test is more sensitive and can offer more information than a home urine test. You may have a qualitative hCG test to measures hCG in your blood. The results are very clear: yes, you're pregnant because we found hCG or, no, you're not pregnant because we didn't find it. The quantitative hCG blood test will actually show how much hCG is in your blood. This is the type of blood pregnancy test that most people are referring to when they talk about blood tests for pregnancy.

Results from quantitative tests give your doctor or midwife not just a yes/no result. They provide measurements that can be compared. In general, your hCG will nearly double about every two days in early pregnancy. So by having multiple blood tests about 48 hours a part, you can track this hCG number and get a better read on the pregnancy. These serial blood tests can help your practitioner monitor your pregnancy for miscarriage or or ectopic pregnancy aw well as the possibility that you’re carrying multiples.

Due to stress, expense and other factors, these tests are not done routinely for every pregnant woman. Talk to your doctor or midwife if you think that a blood test for pregnancy is right for you. Otherwise, you should be able to rely on the results of your home pregnancy tests (HPT).

Source:

Obstetrics: Normal and Problem Pregnancies. Gabbe, S, Niebyl, J, Simpson, JL. Fifth Edition.

Readers Respond: How did you feel in early pregnancy?

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