What is a pregnancy test? Pregnancy testing determines whether a woman is pregnant by detecting chorionic gonadotropin (HCG) in her urine. HCG is a hormone secreted in large amounts by the embryo, starting from about the 7th day after conception. As pregnancy progresses, HCG levels gradually increase, so urine testing can be done to determine whether you are pregnant. When can I take a pregnancy test? The best time to take a pregnancy test is when you are expecting