A pregnancy test looks for the hormone known as human chorionic gonadotropin (HCG). HCG is secreted by the developing embryo after conception. It appears in the blood stream and in urine ten days after fertilization. HCG is responsible for stopping menstruation and for preparing the body for conception. It supports maintenance of the corpus luteum , which secretes progesterone which is essential for the maintenance of the pregnancy. High HCG levels have also been linked to morning sickness in early pregnancy.
Pregnancy tests look for HCG in blood or urine
A blood pregnancy test can be qualitative or quantitative. Qualitative pregnancy tests check whether or not HCG is present. Quantitative pregnancy tests, on the other hand, check how much HCG is in the bloodstream. A blood test will give you a conclusive result in a couple of hours.
In a urine pregnancy test, a sample of your urine reacts with a chemical strip. You have to wait only two minutes for the results to show. The chemical strip contains artificial anticlonal antibodies that react to HCGs. Whenever HCGs are present in the urine, the antibodies discolor the strip. This is the line you see indicating you are pregnant. You can also tell how far along the pregnancy you are by looking at the color of the strip. The darker it is, the more concentrated the HCG levels and the further along you are.
Urine pregnancy tests are most accurate one week after a missed menstrual cycle. Some may get results earlier than 7 days but studies have shown the longer you wait after a missed period to take the test, the higher your HCG levels and the more accurate the result.
It is better if you take a minimum of two urine pregnancy tests. A positive result is almost always accurate. This is not the case for negative pregnancy test results. Test yourself again two days afterwards, just to confirm the result. You might have done the test so early that your HCG levels were not yet detectable. Urine pregnancy kits can only detect a pregnancy if the HCG levels are at least 25-50 mIU/mL. HCGs double every forty-eight hours if you are pregnant. Try again a few days later. You might be pleased with the result! Most manufacturers now pack two or more pregnancy tests together in one kit. Not only do you get better value for your money, you also get to do the test more than once!
If you are pregnant but your HCG levels do not rise accordingly, there may be a problem. Abnormal HCG levels may mean a miscarriage or an ectopic pregnancy. If your HCG levels are extremely high, you may have a molar pregnancy.
It may also mean that you are bearing more than one fetus – twins maybe! A positive home pregnancy test should always be followed up by a blood pregnancy test at your doctor’s clinic.
Blood pregnancy tests are more accurate than urine pregnancy tests. They can also detect pregnancies earlier. The accuracy of a lab result depends on the facilities, procedure and technique used to perform the test.
At-home pregnancy kits are typically 97% accurate but this largely depends on how the test was done.
Popular pregnancy tests
Some popular pregnancy test kits available are First Response Pregnancy Test Kit, Clear Blue Easy Pregnancy Digital Test, e.p.t. Pregnancy Test, Answer Pregnancy Test and Fact Plus Pregnancy Test.
Some fertility drugs may give you a false positive result because they can cause HCG hormones to be present in the body. Prescription drugs, alcohol and other substances tend to have no effect on the result.
What’s your favorite pregnancy test? How many pregnancy tests have you used? Did you ever get a false-positive or a false-negative result? Would like to hear from you.
© 2011 Iva Keene and Natural Fertility Prescription
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