Pregnancy Test

Most pregnancy tests are rather unassuming little bits of plastic and absorbent material. The information they provide, however, can be life changing.

When a woman becomes pregnant and a fertilized egg implants into her uterine wall, she begins to produce a specific hormone – human chorionic gonadotropin, or hCG. This hormone can be found in the urine and blood of a pregnant woman. Initially, the amounts are quite low, but they continue to rise as the pregnancy advances, doubling every two to three days. Home pregnancy tests operate by looking for the presence of hCG in the woman’s urine.

For a pregnancy test to be accurate, enough time must have elapsed between implantation and testing for measurable amounts of hCG to be present in the woman's urine. For most women and most home pregnancy tests, this is about the time of the woman's first missed period – or about 10 to 12 days after ovulation. Some pregnancy tests are able to detect smaller amounts of hCG than others – a quick Internet search can turn up a list of the various tests available for home use and their sensitivity. Generally, they closer you are to the date of the missed period, the more accurate your results will be.

However, because initial amounts of hCG can be very small, you can sometimes get a false negative on an early pregnancy test. A false negative means that the test doesn’t detect your pregnancy, although you are, in fact, actually pregnant. If you receive a negative result and your period doesn’t begin in about a week, take another test. If this test is also negative, you may want to consult your doctor.

In addition, it’s important to note that there are almost never false positives on home urine pregnancy tests unless the woman has been taking hCG as part of a fertility regimen, and there are no other fertility medications that will produce a false positive. If you are taking reproductive hormones, your health care provider can tell you how long it will take the hCG you’re taking to leave your system and when a pregnancy test will give you accurate results.

The technology of the home tests is essentially identical to that of the tests used in doctor's offices, the chief difference being that doctor's offices regularly run control tests to ensure that their tests are providing accurate results. At home, you can increase your chances of having an accurate and reliable result by checking the expiration date on your test and properly following the test directions. Many tests actually include a control line that will show up to indicate that the test is working properly.

To use the test, you’ll need a urine sample. Ideally, you should wait overnight or at least four hours before collecting your urine and most tests call for a midstream sample. This means that you urinate a small amount, and then hold the testing stick in your urine stream. Other tests call for you to catch your midstream urine in a clean cup, then submerge the absorbent tip of the test into the urine for 10 to 15 seconds. For best results, follow the specific directions found on the test you purchased.

The directions will also tell you when to read the test, and what to look for. The display you’ll see if the result is positive will vary based on the brand of test you’re using. For example, in some tests, a dark control line followed by a faint positive line means that small amounts of hCG are present, while others demonstrate pregnancy with a plus sign or a smiley face icon. If you’re uncertain of your results, you can always wait a few days and test again or consult your doctor.