Your Guide to Pregnancy Tests

Home pregnancy test

"Am I pregnant?" is one of the most important questions a woman can ask. And you want to get the correct answer quickly.

Today's at-home pregnancy tests are virtually fool-proof and almost as accurate as those given at the doctor's office. But there are some important issues to consider when deciding what kind of pregnancy test is right for you.

At-home pregnancy tests

According to most manufacturers, at-home pregnancy tests are about 99% effective when used as instructed. That's about the same accuracy rate as most urine pregnancy tests performed in a doctor's office. The tests are available in most pharmacies and do not require a prescription.

One advantage of the tests is that they allow you greater privacy and flexibility in finding out the results. You can take them anywhere there's a bathroom, and they generally take only a few minutes.

At-home pregnancy tests consist of placing a drop of urine on a prepared chemical strip or placing the strip in the urine stream. The strip is designed to detect a pregnancy hormone called human chorionic gonadotropin (hCG).

hCG is released into the body by the placenta when a woman is pregnant. This hormone is also responsible for causing some of the initial symptoms of pregnancy such as breast tenderness and nausea.

hCG levels usually become detectable in the urine about 10 days after conception. That means that if you take a urine pregnancy test less than 10 days after conception, the at-home tests may give a false negative response. This means it will show you are not pregnant when you in fact are.

Experts say women should wait 5-10 days after their period is officially late before taking the tests to ensure accuracy. If the test is negative, wait a few more days. If menstruation still doesn't begin, take the test again and see your doctor if you have more questions.

Here are some tips to follow when taking an at-home pregnancy test.

• Use your first morning urine when possible (when hCG levels are most easily detected). If not, make sure your urine had been in your bladder for at least 4 hours.

• Do not drink excessive amounts of fluids before the test to increase the volume of urine. This could dilute the hCG levels.

• Read the directions included in the test thoroughly before starting the test and follow every step precisely.

• Some fertility drugs or other medications may interfere with the test results. Check the package labeling for information.

In addition, if there is a problem with the pregnancy, such as an ectopic pregnancy (when the fertilized egg settles in the fallopian tube instead of the uterus), hCG levels may be low and non-detectable by an at-home test. See your doctor if you are unsure about the test's results.

Blood tests

Blood tests to detect pregnancy are rarely done as a routine measure because they are expensive, and the same results can be obtained from a urine test.

Pregnancy tests may also be done using a small sample of blood that is analyzed at a hospital or doctor's office. This blood test not only detects whether a woman has the pregnancy hormone in her body, but can also detect how much of the hormone is present. A blood test to detect pregnancy may be done in special circumstances, such as for women who are undergoing infertility treatment or when a problem is suspected.

These blood tests are slightly more sensitive than the urine tests and can detect very small levels of hCG. That means they can provide a more accurate answer very early on in the pregnancy, within about 9-12 days after conception.

The test requires sending the blood sample to the lab for analysis and may take anywhere from a few hours to more than a day to get the results.

A doctor may also choose to use a blood test to correlate hCG levels as the pregnancy progresses. hCG levels usually double about every 2 days during the first few weeks of pregnancy. If the levels don't rise, it may indicate a problem with the pregnancy. Extremely high hCG levels may mean a woman is carrying twins.

The Cleveland Clinic 2004
The Cleveland Clinic
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