If you have regular menstruation, a urine HCG test before menstruation will not show a weak positive result. The sperm and egg combine to form a fertilized egg during ovulation, and only after the fertilized egg enters the uterine cavity and settles, the trophoblast cells begin to secrete blood HCG, which means that it takes at least 20 days after the coitus for a positive urine HCG result to be detected. Therefore, a weak positive result before the onset of menstruation is most likely due to the fact that ovulation has occurred earlier. It is recommended to analyze the results in conjunction with the time of the last menstrual period and the clinical history. If necessary, the test can be repeated after an interval of two days, and if it is still weakly positive, it is recommended to draw blood to rule out ectopic pregnancy.