The home pregnancy test (HPT or urine pregnancy test) 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 the time of implantation, on average 9 - 10 days after ovulation.
With most current pregnancy test kits, hCG can be detected in the urine as early as 4-5 days after implantation, although it often takes longer. Hence, there is nothing to worry if the HPT tested positive 12 days after the day of ovulation/ conception.
Pregnancy tests commercially available now have achieved a very high level of sensitivity and specificity and false-positive results due to interfering materials are extremely unlikely.
These Q&A’s are for educational purposes and should not be relied upon as a substitute for medical advice you may receive from your physician. If you have a medical emergency, please call 911. These answers do not constitute or initiate a patient/doctor relationship.