Test strips for 1-7 days of pregnancy can be detected by some women, while others do not give a positive result. The test measures the level of human chorionic gonadotropin (HCG) in the urine. Normally, HCG levels begin to rise in the blood after the formation of a fertilized egg, and then begin to appear in the urine. Between 1 and 7 days of pregnancy, when the pregnancy is new, HCG may not be present in the urine or levels may be low, and not everyone will have a positive test result. For women with short and regular cycles, it may be possible to detect it, but for women with long and irregular cycles, it is not certain. A positive test can be used to determine if you are pregnant. A blood test for HCG is taken at 31 or 32 days after menopause to determine pregnancy, and blood HCG is more sensitive than urine HCG. In addition, ultrasound is the gold standard for detecting pregnancy. If you find a gestational sac in the uterus through ultrasound, you can be sure that you are pregnant in the uterus. If the preliminary judgment of pregnancy should go to the regular hospital for further examination to confirm the diagnosis.