Whether you've been enduring the two-week wait or you're taken by surprise by a missed period, you know it's time to take a pregnancy test. But wait, is that a faint line you see? Reading a home pregnancy test can be confusing, and if you're really wanting to get pregnant (or hoping to not be pregnant), it's nerve-wracking when you can't tell an evaporation line from a faint positive.
What is an evaporation line on a pregnancy test?
An evaporation line (or "evap line") is a faint line on a pregnancy test that shows up after urine dries on a testing strip.
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"You can see it if you wait too long to read the results," says Layan Alrahmani, M.D., a board-certified ob-gyn and maternal-fetal medicine specialist, clinical faculty and assistant professor at Loyola UniversityOpens a new window in Chicago, and member of the BabyCenter Medical Advisory Board.
Because it can be hard to tell the difference between a faint positive and an evap line on a pregnancy test, it's important to carefully follow the testing kit instructions.
How does an evaporation line compare to a faint line on a pregnancy test?
If you're very early in your pregnancy, the line on certain tests may look less clear than if you're further along. There's even a BabyCenter Community groupOpens a new window dedicated to analyzing pregnancy test photos to distinguish faint positives from evap lines.
So how can you tell the difference between a faint line and an evap line?
"It's sometimes hard!" says Dr. Alrahmani. While a true positive pregnancy test will contain some color, an evap line will be colorless. "Evap lines may be fainter, and in a different spot than where you would expect the pregnancy test [results]," she explains.
How can I avoid an evaporation line on a pregnancy test?
Generally speaking, you'll need to read pregnancy test results within 5 to 10 minutes of peeing on that stick to reduce the chances of seeing an evap line in your results.
That isn't a lot of time, which makes it easy to go over the limit – especially if you get distracted by your phone, your partner, or another child while you're waiting. So set a timer for the suggested wait time right after you take the test, and check the results as soon as your alarm sounds. If you're not sure how long it's been since you took the test and your results look inconclusive, you can always repeat with a new test to double-check.
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Here are a few other tricks to reduce the odds of an inaccurate pregnancy test result:
- Avoid the temptation to test early – wait until the first day of a missed period. Testing too soon can result in false negative results.
- Don't use an expired test.
- Carefully read and follow the instructions that come with your test.
- Take the test first thing in the morning, since that's when the pregnancy hormone hCG in your urine is most concentrated.
What to do if you get an evap line on a pregnancy test
If you think you got an evap line on a pregnancy test because you waited too long to read the results, you can test again right away, says Dr. Alrahmani. Still unsure? Wait a couple of days and test again.
Or, you can make an appointment with your doctor or at a local health clinic for a blood pregnancy test. Blood pregnancy tests can detect even very small amounts of hCG, so they're more sensitive than urine tests. But they're less convenient, and results take longer to come back, so they're not as frequently used.
