A pregnancy test is used to determine if you are pregnant by detecting human chorionic gonadotropin in human urine. Human chorionic gonadotropin usually appears in the urine a few days after the fertilized egg has been laid and can only be detected when it reaches a certain amount. For women who usually have normal menstrual cycles, the test can be done after 7-10 days of delayed menstruation. For women who usually have long menstrual cycles or abnormal ovulation, it can be detected only after 40-44 days of menopause. Human chorionic gonadotropin is secreted by the female placenta and is distributed throughout the body with the blood, so there is a certain concentration of human chorionic gonadotropin in the urine. The morning urine has a higher level of chorionic gonadotropin and therefore the results are more accurate if the pregnancy test is taken in the morning. False positives and false negatives can occur with pregnancy test measurements. If you want to take a pregnancy test with a stick, it is best not to drink a lot of water before the test to avoid dilution of urine and false negatives. Some drugs and diseases can also affect the accuracy of the pregnancy test stick and make the results appear false positive. It is recommended that women can go to the hospital for examination to exclude the corresponding diseases before using it. The pregnancy test stick is not 100% accurate, so it is recommended to go to the hospital in time for early pregnancy checkups, through blood tests and ultrasound, which can not only determine the pregnancy week of the fetus, but also determine whether there is ectopic pregnancy.