Pregnancy Test - Earliest Positive

Q: I am doing a home pregnancy test. When is the very earliest that it could be positive?

A: The urine pregnancy test (home pregnancy test=HPT) checks for the presence of the pregnancy hormone hCG in the urine. hCG is made by the implanting blastocyst and first appears in the maternal blood around implantation, on average 9 days (range: 6-12 days) after ovulation. Blood hCG levels then rise rapidly to reach a peak at 7-10 weeks. They decline after that time. With most current pregnancy test kits (sensitivity 25 mIU/ml), hCG can be detected in the urine as early as 3-4 days after implantation, though it often takes longer. If you are pregnant, on the day you miss your period about 74% of HPTs will be positive. So a negative pregnancy test is normal in about 26% of all pregnancies, and you may have to retest until you know the results. A negative HPT result 10+ days after the missed period makes a pregnancy unlikely. With the present generation of test kits, false-positive results due to interfering materials are extremely unlikely. Pregnancy tests have now reached a level of sensitivity and specificity that is unlikely to be surpassed either by better tests or alternative technology. 

Read more about pregnancy tests HERE.