Home pregnancy tests

Description
Pregnancy begins as soon as an egg is fertilized. Soon, the placenta (which nourishes the fetus in the womb) begins to develop. The placenta secretes the hormone human chorionic gonadotropin (hCG), which can be detected in your blood and urine. HCG disappears from your system when the baby is born.
Pregnancy tests detect hCG in your blood or urine. Years ago, these tests were only done in labs. Today, however, a variety of over-the-counter home pregnancy tests are available. Some home tests can detect hCG in your urine as early as the first day of your missed period. When used correctly, most home pregnancy tests are 95 percent accurate in detecting pregnancy by the tenth day after a missed period.

Some blood tests done at a doctor's office can detect pregnancy as early as three to eight days after conception. However, these tests are usually reserved for specific situations, such as detecting pregnancy in a woman with a history of early miscarriage.


Indications
You may want to take a home pregnancy test if you suspect you're pregnant. Early signs of pregnancy may include:
late or missed menstrual period
breast tenderness and swelling
nausea or vomiting (often referred to as morning sickness, but may develop anytime during the day or night)
frequent urination
excessive fatigue

Patient preparation
The procedure for home pregnancy tests varies depending on the manufacturer. First, read the instructions thoroughly. If you're unsure of the steps, call the manufacturer for clarification. A toll-free customer service number is typically included on the package or in the instructions.
It's especially important to do the test no sooner after your missed period than recommended. Also, remember to check the expiration date on the package -- an expired kit may not provide an accurate result.


Procedure
Follow the manufacturer's instructions completely. The accuracy of the result depends on it. With most tests, you'll place a special stick in a collection of urine or directly in your urine flow. An indicator on the stick will change color or shape depending on whether hCG is detected. The result is often available within minutes. Most tests can be done at any time of the day, but some manufacturers recommend using the first urine of the morning for the most accurate result.
If you're color-blind or have other visual problems, you may want to ask for help in reading the result. Promptly discard used kits, and store unused kits out of the reach of children.


Postprocedure care
If the test is positive, consult your doctor to confirm the pregnancy and begin prenatal care. Avoid alcohol, tobacco and other drugs, and talk to your doctor about using any over-the-counter or prescription medications or herbal supplements or teas during pregnancy. Seek medical care immediately if you develop vaginal bleeding or abdominal pain.
Negative results are less likely to be accurate than positive results. Low levels of hCG may not be detected in early pregnancy or if the test is done too soon. Also, ectopic pregnancies (when the fertilized egg develops outside the uterus) produce lower levels of hCG. Of course, human error is also a factor (not following the instructions or diluting your urine by drinking excessive fluids before the test, for example).

Consult your doctor if you have consistently negative test results and still don't get your period. To verify a negative result, your doctor may consider the date of your last period and do another urine or blood test. You may need other tests, such as an ultrasound (using sound waves to create an image of internal body parts). Pregnancy can be detected as early as three to four weeks after conception with ultrasound.


Benefits
Home pregnancy tests are available without a prescription, and you can take the test in the privacy of your own home. Because you don't have to schedule the test with your doctor, you may be able to learn that you're pregnant earlier and make any necessary lifestyle modifications immediately.

Risks
Again, most home pregnancy tests are 95 percent accurate in detecting pregnancy when used correctly. A positive pregnancy test is a reliable prediction of pregnancy. A negative test, however, should be interpreted cautiously. Depending on the circumstances, you may actually be pregnant.

Considerations
In addition to human error, a number of factors may influence the accuracy of home pregnancy tests. Medications that may affect the results include:
promethazine (brand name Phenergan)
certain seizure medications
certain tranquilizers
diuretics (which dilute the urine)
Certain medical conditions may also affect the results, including:

a pregnancy or miscarriage within the last eight weeks
an ectopic or otherwise abnormal pregnancy
certain cancers
Consult your doctor if you're taking medication or have a health condition that may interfere with the result of a home pregnancy test.