When you finally spy those two lines on a pregnancy test you’ve been wishing oh-so-hard for, you’re bound to be absolutely elated. But when you lovingly look at the test a few hours later (or even the next day), you might be shocked to see that one of those dear little lines has started to fade, or (gasp) has completely disappeared. Try not to freak out, because vanishing lines on a pregnancy test can happen, and here’s why.
How a pregnancy test works
Before you start shaking that stick like an Etch-A-Sketch, it’s important to understand how a pregnancy test works. When you’re pregnant, your body produces a hormone called human chorionic gonadotropin (hCG). Typically, hCG is found in the body when a fertilized egg attaches itself to the lining of the uterus. A pregnancy test can detect the hCG hormone — and if two lines appear, voila, you can be pretty sure you’re pregnant. The next step, of course, is to call your OB-GYN or health care provider so they can confirm the pregnancy.
Reason #1 for vanishing lines: Testing too early
That second pregnancy test line can disappear for a number of reasons Dr. Kameelah Phillips, an OB-GYN, tells Romper. The biggest one is that you just couldn’t quite wait long enough and may be testing a little too early. “If the pregnancy is very early, the hCG level in your urine may just meet the threshold for being detected,” explains Phillips. “You will see a faint line that can disappear over time.” Most home pregnancy tests will suggest a time frame for testing, and if you’ve been tracking your cycle, you should have a rough idea of when the best time to test is. If you test early, that’s OK, just know that the results may not be completely trustworthy.
The study “Accuracy of home pregnancy tests at the time of missed menses” found that in order to get the most spot-on result, the hCG concentration in urine has to be around 12.5 mlU/mL to get a 95% accurate reading — and only one in the 18 pregnancy tests used in the study had that sensitivity. So, wait a little while longer so that you get the right result the first time.
Reason #2: Your home pregnancy test is old
Another reason why your pregnancy test result changes seemingly overnight might have nothing to do with you, but rather the age of your test itself. “Although the issue of the disappearing second line is unusual, you can see it if the test is an old test kit which could have dried out over time,” Dr. Mary Jane Minkin, a gynecologist, tells Romper. “I usually recommend to my patients to use an active test kit.” If you’re not sure if yours is still active or not, you should always look at the pregnancy test’s expiration date (and yes, they do have one, Healthline reported) to ensure it will give you the most accurate results.
Reason #3: You waited too long to read pregnancy test results
Waiting to see if your pregnancy test result is positive or negative can be the longest minutes of your whole life. But, even if the anticipation is nerve-wracking and exhilarating at the same time, try not to wait too long to read the results, Phillips advises. “If the test was weakly positive, then a faint line can fade if left too long before interpretation,” she says. “It is important to interpret the results during the recommended time frame.” So, even though all you might want to do is pee on the stick already, just know how long your test result will be accurate before it could potentially change. And if you’re not sure, you can always take another test.
Reason #4: You might have miscarried
Yes, sometimes, you might get a positive result, and then take another test the next day (or within a few days) and not see that second line because of a chemical pregnancy. A chemical pregnancy, also known as a biochemical pregnancy, is a term that’s often used to describe very-early pregnancy loss (before or near 5 weeks). And because some tests are so sensitive, they might be able to pick up on the pregnancy hormones despite the fact that you’re no longer pregnant. “When you have a miscarriage, the levels of hCG drop, then, over time, the intensity of the line will fade,” Phillips explains.
If you’ve taken a pregnancy test that has turned from positive to negative, try not to panic (easier said than done). You can always retest in a day or two with a fresh, new test, or even contact your OB-GYN to get a blood test for some certainty. That way, you’ll know the real results and can plan accordingly.
Cole, L. Khanlian, S., Sutton, J., Davies, S., Rayburn, W. “Accuracy of home pregnancy tests at the time of missed menses” 2004.
Dr. Kameelah Phillips, MD, an OB-GYN
Dr. Mary Jane Minkin, MD, Clinical Professor of OB-GYN at Yale
Dr. Kim Langdon, MD, an OB-GYN
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