Topic: Causes of a False Positive Pregnancy Test
Maybe you can’t wait to have a baby. Or maybe that’s the last thing you’re hoping for.
Either way, if you think you might be pregnant, you need to know for sure. But what are the odds a positive pregnancy test might be wrong?
“Home urine pregnancy tests are pretty reliable,” says Ob-Gyn Jonathan Emery, MD. “But there are some reasons you might get a false-positive result.”
Dr. Emery explains when and why a pregnancy test might give a false positive — and what you can do to make sure the stick doesn’t lie.
How do pregnancy tests work?
When you get pregnant, your body produces a hormone called human chorionic gonadotropin, or hCG. Home pregnancy tests look for that hormone in your urine. If hCG is present, you should get a positive test result when you pee on a stick.
But hCG levels start out very low and increase over time. If you take the test too soon after conceiving, it might say you’re not pregnant when you really are.
In other words, timing can lead to a false negative. But what about a false positive?
Chances of a false positive pregnancy test
alse positives aren’t super common, Dr. Emery says. But they’re not impossible. Some potential causes include:
Early miscarriage or chemical pregnancy
You took a pregnancy test and got two lines. (Positive!) But a few days later, your period arrived in force. What gives? The most common reason this happens is an early pregnancy loss, also known as a chemical pregnancy. In this case, the test was accurate — there was a pregnancy, but it wasn’t a viable one, Dr. Emery explains.
“It’s not technically false since a very early pregnancy did occur,” he says. “But this is the most common reason that a pregnancy test might appear to have been false.”
“A lot of fertility treatments involve taking hCG injections,” Dr. Emery says. If you’ve been taking fertility medications, that hCG might still be floating around your system.
That could trigger a positive pregnancy test, even if you’re not pregnant. To avoid that mix-up, wait at least two weeks after your last hCG injection to take a home pregnancy test, he says.
Topic Discussed: Causes of a False Positive Pregnancy Test