Why Did a Second Line Appear Later on My Pregnancy Test?

Understanding how pregnancy tests work is key to interpreting the results. When you take a home pregnancy test, you look at the results window to see whether there are two lines or just one. The first line is the control line. If that's all you see, your result is negative. But two lines in the testing window mean that you're pregnant.

Pregnancy test results are only valid for 10 minutes. Sometimes, however, you may get a negative result, then look at the pregnancy test later in the day to see that a positive line has magically appeared.

There are a few reasons why this can happen. However, in most cases, the original reading of the test ("not pregnant") is typically the correct one. Here's what you need to know about a delayed second line on a pregnancy test.

How Do Pregnancy Tests Work?

Home pregnancy tests measure a hormone called human chorionic gonadotropin (hCG) in your urine. Your body starts producing hCG after a fertilized egg implants itself in your uterus, about six to ten days after ovulation. Your body only produces hCG during pregnancy, so even the faintest suggestion of a second line indicates that you have likely conceived.

To take a pregnancy test, direct your urine stream over the stick or collect your urine in a sterile container and dip the stick into it for about 20 seconds. Check the test again in about three minutes to see whether one or two lines appear. Note that different tests have different instructions, so you should always follow the manufacturer's instructions for your specific test.

Interpreting Pregnancy Test Results

You can say for sure that you're expecting if you see a positive result on your pregnancy test within 3 to 10 minutes. Remember that it doesn't matter how faint that line is, because your body only produces the pregnancy hormone hCG while you're pregnant.

Sometimes you'll see a faint line if you test on the earlier side and the hCG is still building up in your system. A line that gets progressively fainter over days of testing may indicate that you're miscarrying, so reach out to your provider if this happens.

What Happens If a Positive Line Appears Later?

The instructions on most pregnancy tests will advise you to read the results within a certain window of time. This usually spans up to 10 minutes. If you see a positive result beyond this time frame, you may be left second-guessing the results.

However, always remember that a pregnancy test result is only accurate within 10 minutes. After that, it's best to throw the test away to avoid confusion.

Am I Seeing Evaporation Lines?

If urine splashes onto the pregnancy test window, it can dry and leave streaks. If one of these streaks appears around the spot where a positive result would appear, it can look like a second line.

The easiest way to differentiate between a positive test result and evaporation line is to check your test within the allotted time. A true positive will appear within two to 10 minutes, while urine won't dry and form streaks until some time later.

What If My Positive Line Is Faint?

If you follow all of the instructions correctly, you may notice a thin, faint pregnancy test line that appears within a few minutes. There are several possible explanations for this line's faintness.

• You may have taken the test too early in your cycle. If you test earlier than 10 to 12 days past ovulation, the hCG hormone may not be high enough to produce more than a very faint line. The best time to test is after your period is late, or 2 weeks after you ovulated.
• Your urine might be diluted, skewing the test's results. You can dilute your urine sample if you're drinking too many liquids; this is why experts recommend testing first thing in the morning.
• Some pregnancy tests have lower sensitivity levels, so they'll show fainter lines earlier on. Although it's not necessary, you can try retesting with a different type of test if you want to see a darker line. Look for "early results" indicated on the test label. Be sure to also check the pregnancy test expiration date.
• If your positive result is appearing lighter each day, this could mean that you are having an early miscarriage.

Remember that many factors can impact how light or dark your positive line is, such as using different test brands, drinking different amounts of fluids, or testing at different times of the day. Reach out to your health care provider if you have any concerns about your pregnancy.

False Negative Pregnancy Test Results

While it's nearly impossible to get a false positive result, false negatives can certainly happen. Even if you're pregnant, your hCG levels may sometimes be too low for detection in your urine. This is more common if you test before your period is due, but it can also happen right around the time of your missed period.

Many of the same factors that cause a faint line can also cause a false negative, such as diluted urine or lower sensitivity tests. If you still haven't gotten your period, wait a few days and test again. HCG builds rapidly in your system, so you may see a positive soon after seeing a false negative.

Always use a sample from your first-morning urine (which is more likely to have higher concentrations of hCG.

How to Handle a Positive Pregnancy Test

If you get a positive pregnancy test, contact your health care provider or search for an OB-GYN in your area. They'll likely ask you to come in sometime around 7 weeks past the first day of your last menstrual period. At this visit, your provider will conduct an ultrasound to confirm the pregnancy.

If your test is negative, wait for your period to come. If you want to get pregnant, you can start trying again shortly thereafter.

If you take a pregnancy test and you're not sure what it's telling you, you can always test again the next day, or see a doctor for a pregnancy blood test. Sometimes this is the best way to get rid of any stress surrounding a confusing test result.