While at work yesterday, I had a young lady approach me with a question about home pregnancy tests.  She had taken a home pregnancy test which came back with a positive result, but when she went to see her doctor to confirm the result, her tests came back negative.  She was wondering how she could get a positive result on the home test without being pregnant (this is called a false positive). 

 

First, a little background on the tests!  Home pregnancy tests are built to detect the hormone called human chorionic gonadotropin (HCG) in the urine.  Between 5 to 10 days after the egg becomes fertilized by the sperm (at this point it’s called a zygote), the entire process of implantation takes place.  Once the zygote attaches to the lining of the uterus (implantation), the placenta is made – the placenta is what produces the HCG.

 

A false positive may have occurred if:

 

1)    She let the test sit for too long.

 

2)    She had a urinary tract infection (UTI) caused by a specific bacteria.

 

3)    She had been taking certain drugs like HCG shots for infertility treatment, anti-convulsants, certain diuretics, and certain drugs to treat Parkinson’s disease. 

 

4)    The pregnancy was caught early, but she ended up going on to have her period due to early miscarriage.

 

Home pregnancy tests are fast, easy to perform, and about 97% accurate when used correctly.  It is always best to do two tests no matter what the result is just in case you made an error.  If you come up with positive results, please be sure to follow-up with your doctor as soon as you can!