Pregnancy Tests

Pregnancy tests work by detecting human chorionic gonadotropin (hCG) which is a hormone released just after the embryo attaches to the uterine wall.  The levels of hCG increase rapidly over the following days.  The pregnancy tests that you take at home measure the hCG in the urine while a doctor can also perform a blood test.  The most sensitive urine tests can detect a pregnancy one day after a missed period.  It is recommended however to wait 5-10 days after your period is due to maximize the opportunity for the pregnancy test to detect the hormone.  Blood tests are far more sensitive than urine tests, but generally not necessary unless there is cause for concern. 

False results can happen with home pregnancy tests.  If the test is designed to detect a level of hCG that is too high it can yield a false negative.  False positives can result from certain medications which contain the pregnancy hormone like Pregnyl, Profasi, Pergonal, and Humegon.  Negative tests can also occur due to human error so read and follow the instructions carefully.

The major difference between one pregnancy test and another is their sensitivity and how low the measurable levels of hCG may be.  The technology behind home pregnancy tests and improved dramatically over the years and there is less opportunity for human error.

Home pregnancy test kits are sufficient to diagnose a pregnancy; the key is to wait as long as possible so that your body has a chance to produce a sufficient amount of the hCG hormone so that the test is able to detect its presence.