Pregnancy Test
Questions about Home Pregnancy Tests
The importance of human chorionic gonadotropin (hCG).
If you think you might be pregnant, there are tests you can use to find out. They all work by detecting the hormone human chorionic gonadotropin (hCG), which is present in blood and in urine. hCG is produced in increasing amounts during the first trimester, after an embryo implants in the uterus. After that it decreases.
The urine test is readable at 12-14 days. This is when the hCG level is high enough for the color change to be visible.
Blood tests can tell if you are pregnant in 6-8 days.
There are two main types of pregnancy tests. One type tests your urine for hCG, and another tests your blood. Several brands of urine home pregnancy test (HPT) are available over the counter from drugstores or supermarkets. To get a blood test, you must see your doctor.
HPTs have chemicals, usually on a stick, that change color in response to hCG. Usually the change is represented in a line. If the line appears after about 10 minutes after contact with urine, you are pregnant.
The accuracy of an HPT is dependent on:
- How closely you have followed the instructions.
- How long it has been since implantation has occurred. Time to implantation is variable among women, so sometimes there is not enough hCG in your system to cause the color change reaction. If you think you are pregnant, but the test is negative, wait a few days and try the test again (most HPTs come with two tests).
- The brand of test. Some are more sensitive than others and can detect lower levels of hCG. (Some studies and reviews have suggested that First Response™ is the most sensitive test.)
This all means that you could be pregnant even if a HPT says you are not. False positives (a test that says that you are pregnant when you are not) will not occur unless for some reason you are taking medication containing hCG (which are generally used only for
fertility treatment, because you are trying to get pregnant). Other drugs and alcohol do not affect pregnancy tests.
If you get a positive home pregnancy test, you should see your doctor. Your doctor will confirm your pregnancy with a more sensitive test, and do an exam. It is very important for the health of your baby to see your doctor early in your pregnancy. You should also continue to see the doctor regularly, on the schedule that prescribed.
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