If you’re trying to conceive, there’s nothing more exciting than a positive pregnancy test. You did it, you’re pregnant! Unless you’re part of the unlucky minority who had a false positive pregnancy test. Home pregnancy tests are 97% accurate, and while that’s not perfect, that’s still a pretty good average. A home pregnancy test measures the amount of human chorionic gonadotropin (hCG) in a woman’s urine. The pregnancy hormone is produced after a fertilized egg successfully implants in the uterus. “A urine test needs 50 units of hCG to test positive,” explains Daniel Roshan, M.D., an OB-GYN at Rosh Maternal-Fetal Medicine in Manhattan. So what can lead to a false positive? There are actually a few different reasons for what can cause a false positive pregnancy test.

1. Early miscarriage

Sometimes, a woman is pregnant when she takes a pregnancy test, only to have a heavy period a few days later. This is often the sign of a miscarriage, or chemical pregnancy. A chemical pregnancy is an early pregnancy loss that occurs shortly after implantation. Chemical pregnancies take place before ultrasounds can detect a fetus, but not too early for a pregnancy test to detect levels of hCG.

It’s estimated that chemical pregnancies may account for 50% to 75% of all miscarriages.

2. Medications and fertility treatments

Some medications can lead to a false positive pregnancy test. If you’re taking anti-anxiety meds, anticonvulsants, antihistamines, or diuretics, these can all influence a pregnancy test. During fertility treatments, some women receive injections of hCG to stimulate ovulation. Anyone in this situation should ask her doctor how to properly test for pregnancy.

3. User error

pregnancy tests for everyone!

It’s actually really important that you read the directions on a home pregnancy test. Some tests require the stick to be placed into the urine stream, while others need to be dipped into a cup of urine. Don’t test too soon! Tests are more accurate after a missed period. Also, pregnancy tests actually expire! Make sure you check the date on the box before you test.

No matter what, if you get a positive pregnancy test you should make an appointment with your doctor. Only she will be able to confirm if you truly have a bun in the oven!

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(Image: iStock / Highwaystarz-Photography)