Home pregnancy tests can find the presence of a pregnancy hormone (called human chorionic gonadotropin, or hCG) in a sample of urine. High levels of hCG are made during pregnancy. The home tests have similar results to the pregnancy tests done on urine in most health professionals' offices if they are used exactly as instructed.
When a woman becomes pregnant, the egg is generally fertilized by a sperm cell in a fallopian tube (conception). Within 9 days after fertilization, the egg moves down the fallopian tube into the uterus and attaches (implants) to the wall of the uterus. When the fertilized egg implants, the placenta starts to develop and begins to release hCG into the woman's blood. Some of this hCG also passes in her urine. In the first few weeks of pregnancy, the amount of hCG in the urine gets higher very quickly-it doubles every 2 to 3 days.
There are two basic types of home pregnancy tests.The most common types of home pregnancy tests use a test strip or dipstick that you hold in the urine stream or dip into a sample of urine. An area on the end of the dipstick or test strip changes color if hCG is present, meaning you are pregnant.
A second type uses a urine collection cup with a test device. To use this type of test, you may place several drops of urine into a well in the test device or you put the test device into urine collected in a cup. An area of the device changes color if hCG is present, meaning you are pregnant.
The first urine of the morning (that has collected in the bladder overnight) is the best one to use and has the most accurate test results.
The accuracy of home pregnancy tests are different for every woman because:The days of a woman's menstrual cycle and ovulation can change each month.
The exact day of implantation of the fertilized egg is not always known.
Each home pregnancy test kit has a different sensitivity to find hCG. If the level is very low, the first urine of the morning is the most likely to show a positive result.
While a few home pregnancy tests may be sensitive enough to show a pregnancy on the first day of a woman's missed period, most test kits are more accurate about a week after a missed period.
Home pregnancy kits are available on the Internet.
Why It Is DoneA home pregnancy test is done to detect pregnancy by detecting human chorionic gonadotropin (hCG) in your urine.
How To PrepareYou can buy home pregnancy test kits without a prescription in many pharmacies and supermarkets.
The test kits generally have plastic dipsticks or test strips and instructions that explain how to do the test. Some kits have a urine collection cup and a dipstick that you dip in urine. Midstream kits have a test strip that you hold in your stream of urine for several seconds. All kits tell you to wait a specific amount of time before reading the results.
When to testHome pregnancy kits can be used on the first day of a missed menstrual period. However, the test results are more accurate if you wait a few days longer (~1 week). If you do the test as soon as you have missed a period and the results show you are not pregnant (negative results), repeat the test in 2 week if your menstrual period has not started, or have a pregnancy test done at your health professional's office or a clinic.
General instructionsFor any home test, you should follow some general guidelines:
Check the expiration date on the package. Do not use a test kit after its expiration date-the chemicals in the kit may not work correctly after that date.
Store the test kits as directed. Many kits need to be stored in a refrigerator or cool place.
Read the instructions that come with your test carefully and thoroughly before doing the test. Look for any special preparations you need to take before doing the test, such as avoiding certain foods or limiting your physical activity.
Follow the directions exactly. Do all the steps, in order, without skipping any of them.
If a step in the test needs to be timed, use a clock. Do not guess at the timing.
Many home kits show color changes on a test strip. If you are color blind or have trouble seeing different colors, have someone else read the test results for you.
Record the results of the test so you can discuss them with your health professional.
How It Is DoneCarefully read the instructions that come with the home kit. Instructions vary from kit to kit. Be sure to read the result at the appropriate time indicated in the instructions for accurate results.
If you have a kit that asks for a morning urine sample, test urine that has been in the bladder for at least 4 hours. A first morning urine sample (that has collected in the bladder overnight) gives the most accurate test results. Test the urine within 15 minutes of collecting the sample.
If you are using a midstream kit, urinate a small amount first and then hold the dipstick in your urine stream as you finish urinating. Test the urine sample according to the directions included in the test kit package.
Specific instructionsDipstick test. For a dipstick test, you place the end of the dipstick or test strip into a sample of urine. You will either urinate directly onto the labeled end of the stick for 5 to 10 seconds or put the stick into urine in a collection cup. If you are pregnant, a positive result (a color change or a symbol showing) will appear in that area of the dipstick or test strip.
Collection cup test. For a test that uses a collection cup, you urinate into the cup included with the kit, then collect several drops of the urine with a dropper or syringe. Place 5 or 6 drops of urine directly onto a test disk to complete the test. If you are pregnant, a positive result will appear in a special area on the disk as a color change.
What Affects the TestReasons you may not be able to have the test or why the results may not be helpful include:
Taking the test very early in your pregnancy. HCG may not be found. In this case, the test kit may show that you are not pregnant when you really are pregnant. This is called a false-negative result. If you have drunk a lot of fluid, your urine may be diluted and this may also cause a false-negative result.
Having soap in the urine collection cup. This may cause the test results to show that you are pregnant when you are not pregnant. This is called a false-positive result. False-positive results may also be caused by reading the test at the wrong time, letting the test equipment get warm, having protein or blood in the urine, or having hCG hormone in the urine from some other cause.
Taking certain medicines, such as chlorpromazine hydrochloride (Thorazine) and methadone hydrochloride (Dolophine, Methadose).
Taking fertility medicines that contain human chorionic gonadotropin.
Not reading the result at the right time as shown on the instructions. If you read the result too early or too late, the color change may not be accurate and you will need to retest.
