How Reliable Are Early Pregnancy Tests?

Deciding When to Test to Get the Most Accurate Result

Woman looking at pregnancy test.
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If you think you might be pregnant, you will usually want to know as soon as possible. As more and more home pregnancy tests advertise that they can confirm pregnancy early—even before you miss your period—it's fair to wonder just how soon you can test and still get an accurate result.

Testing Before a Missed Period

A urine-based early pregnancy test works by measuring the amount of ​human chorionic growth hormone (hCG) in urine. Typically, you will need to have missed your period to ensure an accurate result, particularly a positive one. With that being said, if you receive a positive result a couple of days in advance of your missed period, it means that hCG has been detected and that you are, in fact, pregnant.

As pregnancy tests become more sensitive and able to detect even minute amounts of hCG, early results like these may not only become more commonplace but offer greater accuracy in delivering a positive result. But what happens if you receive a negative one?

In this instance, it doesn't mean that you are not pregnant; it simply says that the test is unable to detect any hCG in the urine sample. It may be that there is none to be detected or that the body has not yet produced enough to elicit a positive result.

If you receive a negative result and tested before your missed period, you would need to wait a couple of days before retesting. If your period starts within this timeframe, then there would be no need to proceed. However, your period is light or short, you may still want to get tested. In some cases, conception will be accompanied by implantation bleeding, a condition wherein spotting or bleeding signals that the fertilized egg has implanted. This usually happens 10 to 14 days after conception and is not considered a sign of trouble.

Pregnancy Testing Tips

The desire to know whether you're pregnant is understandably a strong one. But it is important to remember that all tests have their limitations. While many will claim to be capable of detecting pregnancy before your next monthly period, any assertion that they can do so eight days prior is simply unrealistic.

One 2014 study conducted in Germany showed that, of the 15 brands commercially available, no less than 50 percent fell short of their accuracy claims.

Similar concerns regarding inaccurate labeling led the U.S. Food and Drug Administration to issue guidelines advising against the use of the term "greater than 99 percent accuracy" on home pregnancy tests. For that to be true, a test would have to detect hCG at levels as low as 12 mIU/ml when, in fact, many are in the range of 40 mlU/ml and higher.

Even with far improved home testing kits, to ensure the most accurate results:

  • Try to delay testing until the first day of your missed period.
  • Be sure to check the expiration date and follow the product instructions exactly.
  • Wait a full 10 minutes before checking the results window.
  • If the test is positive, schedule an appointment with your doctor to begin prenatal care.
  • If the result is negative and you still believe you are pregnant, wait 48 hours to retest as the hCG level will typically double in that time.
  • Even if the line is faint, in most cases it means that you are pregnant. You can double check in a day or so when hCG levels would presumably be higher.
View Article Sources
  • Gnoth, G. and Johnson, S. "Strips of Hope: Accuracy of Home Pregnancy Tests and New Developments." Geburtshilfe Frauenheilkd. 2014; 74(7):661-9. DOI: 10.1055/s-0034-1368589.
  • Nerenz, R.; Butch, W.; Woldemariam, G. et al. "Estimating the hCGβcf in urine during pregnancy." Clin Biochem. 2015; 49(3):282-6. DOI: 10.1016/j.clinbiochem.2015.10.020.