A blood test to determine pregnancy is performed by checking if human chorionic gonadotropin (hCG, which is a pregnancy hormone) is present. This hormone is formed by the placenta of a pregnant woman and can be found in the blood as well as urine within 10 days of fertilization. Blood tests are more reliable to an extent that they help detect whether or not the woman is pregnant much earlier as compared to urine or other home pregnancy tests. There are two types of blood tests to determine pregnancy and they are the quantitative blood test and the qualitative blood test. The quantitative blood test not only helps in finding out the presence of hCG in the blood but also helps to know the exact quantity of hCG that is present in the blood. Therefore the results of this test are said to be very accurate. On the other hand, a qualitative blood test only helps to identify whether hCG is present or not. A positive result indicates the woman is pregnant and changes in the level of hCG over a period of time in a normal fashion is a sign that the pregnancy will be healthy. Normally, the hCG levels continue increasing the whole of the first trimester and then slowly start going down. Thus, while in the first trimester, a woman can have her blood test done on a regular basis to ensure that the levels are increasing as desired.
This being a blood test, it is carried out by taking a sample of your blood through the vein or by pricking the tip of your finger with a sharp instrument and this sample is sent to the lab for testing. Even though your blood has tested negative for pregnancy there are chances that you may be pregnant. This could be if your blood test was done too early and so the levels of hCG were not sufficient to confirm pregnancy.. There are also a few diseases related to the liver, cancer or other such conditions that can cause the levels of hCG to raise leading to a false positive report. Sometimes, it may also happen that your blood test is positive but you are not pregnant and this is because of the presence of hCG which may have arisen due to the intake of certain medicines that contain hCG. It would therefore be advisable that you get yourself tested again to confirm the results.
Submitted by M T on April 7, 2010 at 11:05