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Sunday, May 19, 2013
There are two types of pregnancy tests; one uses a urine sample, the other a sample of blood. Both tests detect the presence of a hormone called human chorionic gonadotropin (hCG). This hormone is produced by the placenta shortly after the embryo attaches to the uterine lining and builds up rapidly in your body in the first few days of pregnancy.
There are different types of urine tests, and these can be performed at home or in a clinic. The first type of test involves collecting your urine in a cup and dipping a stick into the urine, or putting urine into a special container with an eyedropper. A second type of test involves placing a stick into your urine stream and catching your urine in midstream.
Tests vary in how long you have to wait to get a result. You will be looking for a change in color, a line, or a symbol (like a plus or minus). A new digital pregnancy test offered by Clearblue Easy makes reading your results simple: the window will either show the words "not pregnant" or "pregnant". You can also get recommended midstream urine tests online.
All tests come with instructions, and it is important that you follow these instructions to get an accurate reading.
Here are some frequently asked questions and answers about urine tests:
When can I take a urine test?
Most doctors recommend that you wait until the first day of your missed period before taking a urine pregnancy test. This is usually about two weeks after conception. However, some tests are more sensitive than others and can be taken earlier.
How accurate are urine tests?
Urine tests or home pregnancy tests are around 97% accurate when done correctly. Home pregnancy tests are great to use because they can be done at home, they are usually low in cost (anywhere from $7.99 to $19.99), private, they give a fast result, and are easy to use. However, if not done correctly or taken too early, the result can be inaccurate. If you get a negative result and still have symptoms of pregnancy (missed period, nausea, breast tenderness and fatigue), wait a week and take another test or contact your doctor so you can have a blood test done.
There are two types of blood tests. A quantitative blood test measures the exact amount of hCG in the blood, and a qualitative hCG blood test gives a simple yes or no answer to whether you are pregnant or not.
The advantages of having a blood test done are:
The disadvantages of having a blood test done are:
If I get a positive result on a home pregnancy test, does that mean I am pregnant?
A positive result from a home pregnancy test shows the presence of the hormone hCG in your system. When an embryo implants in a woman's uterine lining or anywhere else in the body (i.e. ectopic pregnancy), hCG hormones are produced. This is a sign that you are pregnant.
If I get a negative result on a home pregnancy test, does that mean I am not pregnant?
A negative result can mean that you are not pregnant, you took the test too early, or you performed the test incorrectly. Pregnancy tests vary in their sensitivity (how soon they can detect the hormone hCG), and you may not have given your body enough time to produce enough hCG hormones that will show up on the test. Also, if you let a test sit for too long (after the instructions on the box tell you), the test is invalid. It is best to follow the instructions and wait until you have missed a period before taking the test. Most pregnancy tests come with two in a box, and it is a good idea to take both.
When is the earliest that I can take a home pregnancy test?
It is recommended that you wait until you have missed a period to take a home test. If you cannot wait that long to find out and you know the day you may have conceived, then the earliest you can take a test would be 14 days from possible conception.
What if I take a couple of home pregnancy tests and get different answers?
If you have received different answers on multiple pregnancy tests, it is recommended that you seek care from a healthcare professional. They may choose to repeat the urine test or to perform a blood test.
How accurate are home tests?
Home tests are very accurate (around 97%) when used correctly. Some kits come with two tests because mistakes do happen. If you take a test too early, you may get a false negative (when the test says you are not pregnant but you are). Your body needs time for the hormone to rise to a high enough level to be detected in a test. If the test comes back negative but you still think you could be pregnant, wait a few days and try again. False positives (when the test says you're pregnant but you're not) are possible, but rare. A positive pregnancy test is a pretty good indication that you are pregnant.
How does a test tell if you are pregnant or not?
A pregnancy test detects the presence of a hormone called human chorionic gonadotropin (hCG) in your blood or in your urine. hCG is produced in the placenta shortly after the embryo attaches to the uterine lining and builds up rapidly in your body in the first few days of pregnancy.
How long do I have to wait before I take a test?
Most doctors recommend that you wait until the first day of your missed period before taking a home pregnancy test. This is usually around two weeks after conception. However, some tests are more sensitive (and more expensive) than others and can be taken earlier. Concentrations of hCG are reported in milliInternational Units (mIU) or amounts equal to 1/1000th of an IU per milliliter. A pregnancy test with a sensitivity of 20 IU/L is more sensitive than one with 50 IU/L. A blood test administered by your doctor is more sensitive than the early home tests and can be taken between seven and twelve days after you conceive.
This article is a NetWellness exclusive.
Last Reviewed: Apr 29, 2009
Arthur T Ollendorff, MD
Associate Professor of Obstetrics and Gynecology
College of Medicine
University of Cincinnati