How long should you wait after sex to take a pregnancy test to get a accurate result?

Very accurate at 3wk: A urine pregnancy test gives a reliable result by 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant, and a test is not needed.