Thank you for the question and thank you for visiting our site. This is a common question and is a valid concern. A pregnancy test will turn positive about two weeks after conception. So, I would not rely on the urine test being able to tell someone how far along they are - it is more important WHEN it turned positive and how long before she had unprotected intercourse and with who. That being said, the ONLY way to reliably give an accurate answer is by knowing her due date. This, combined with the timing / date of the first ultrasound will give a very accurate guestimate of when she conceived. I am happy to help further with this through our paid service and you can ask for Dr. Raichle. I hope that this helps and good luck! Dr. Tim