Accuracy of pregnancy tests

How accurate are home pregnancy tests?

Home pregnancy tests (HPTs) can be quite accurate. But the accuracy depends on:

How you use them — Be sure to check the expiration date and follow the instructions. Wait ten minutes after taking the test to check the results window. Research suggests that waiting 10 minutes will give the most accurate result.

When you use them — The amount of hCG or pregnancy hormone in your urine increases with time. So, the earlier after a missed period you take the test, the harder it is to spot the hCG. Many HPTs claim to be 99 percent accurate on the first day of your missed period. But research suggests that most HPTs do not always detect the low levels of hCG usually present this early in pregnancy. And when they do, the results are often very faint. Most HPTs can accurately detect pregnancy one week after a missed period. Also, testing your urine first thing in the morning may boost the accuracy.

Who uses them — Each woman ovulates at a different time in her menstrual cycle. Plus, the fertilized egg can implant in a woman’s uterus at different times. hCG only is produced once implantation occurs. In up to 10 percent of women, implantation does not occur until after the first day of a missed period. So, HPTs will be accurate as soon as one day after a missed period for some women but not for others.

The brand of test — Some HPTs are more sensitive than others. So, some tests are better than others at spotting hCG early on.