Available over-the-counter at drugstores, home pregnancy tests are cheap, easy, quick tests that tell you whether or not you are pregnant by detecting the presence of the pregnancy hormone, hCG, in your urine. You should always check with your doctor if you get a positive result on a home pregnancy test. Your doctor can confirm whether or not you are pregnant with a blood test and/or a pelvic exam, and start you on a course of prenatal care to assure a healthy pregnancy. Even a negative result on a home pregnancy test is a heads-up to call your doctor to look for possible medical reasons for your missed period(s).
How Home Pregnancy Tests Work
Most home pregnancy tests call for a testing stick or powder to be dampened with urine. Within a couple of minutes, the stick or powder will change appearance, indicating either a positive (pregnant) result or negative (not pregnant) result.
Accuracy and Use
The National Women’s Health and Information Center notes that home pregnancy tests, if used properly, yield very accurate results. To assure accurate results, follow the sampling instructions on the test exactly. Don’t used tests with an expired date. Check your test strip carefully against the results key, keeping in mind that any indication of a positive result, however faded or slight, is a sign to call your doctor.
Accuracy and Timing
The accuracy of a home pregnancy test is also linked to when you take it. Here is why. When you become pregnant, the hormone human chorionic gonadotropin (hCG) is produced in your body starting six days after conception. The concentration of the hormone in your urine is low at first, then becomes higher and more detectable daily. At about a week after your missed period, the hormone is detectable enough to be reliably picked up by a home pregnancy test.
Although you could take the test earlier and perhaps get an accurate positive result, a negative result is suspect. Studies indicate that conception is delayed in 10 percent of women, according to the National Women’s Health and Information Center. If you get a negative result from taking the test less than a week after your missed period, you are advised to take the test again in a few days, to give the pregnancy hormone, if present, time to build up in your body. Also be aware that the concentration of the pregnancy hormone varies throughout the day and is greater in the mornings.
The Mayo Clinic recommends that you request a blood test from your doctor if you need to know whether you are pregnant earlier than a home pregnancy test can accurately detect the hormone.
Accuracy and Variance
Females’ bodies vary in the amount of pregnancy hormone present in their urine. Home pregnancy tests that claim accuracy on the very day of a woman’s missed period may very well be so—for some women, yet not for others.
Accuracy and Brands
Although all home pregnancy tests are designed to detect the pregnancy hormone, their unique design differs enough so that some are highly sensitive and others less so during the earliest days of pregnancy. A 2004 study testing 18 different home pregnancy tests found that only the First Response, Early Result Pregnancy Test, showed consistent sensitivity in detecting low pregnancy hormone levels. Used after a week after the date of the missed period, however, most tests showing positive results proved accurate.
False Positives and False Negatives
The Mayo Clinic reports that when using up-to-date tests, false positive results in home pregnancy tests are rare. If the test says that you are pregnant, there is a very good chance you are, unless your urine contains traces of blood, protein or certain medications or unless the test kit is defective. Getting a negative result is a different matter, and far more common. A false negative suggesting that you are not pregnant when you actually are may occur when the levels of pregnancy hormone in your urine are too low to be detected by the home pregnancy test. If you don’t follow the timing part of the test instructions exactly, you may also get a false negative. Lastly, the Mayo Clinic advises that taking a home pregnancy test in the morning, before drinking anything that might dilute your urine, can help you avoid a false negative. Because false negatives do happen, it is best not to treat a negative result as conclusive. Take the test again in a few days if your period still hasn’t come.