Blood HCG tests are often used to determine pregnancy, and the results are relatively accurate. Occasionally, however, there are cases where the blood test does not detect pregnancy, but ends up with a pregnancy. HCG is secreted by the trophoblast cells after the fertilized egg has implanted in the uterus, and can be detected in the blood on the first day after implantation, which is about 8 days after ovulation. However, as the ovulation period may fluctuate, the detection time may be delayed. If the blood HCG test is performed too early, the elevated HCG cannot be detected in the blood, and therefore cannot be detected during the blood test. Women of childbearing age with history of menopause and sexual life, when menstruation is delayed for more than 10 days, accompanied by symptoms such as loss of appetite, liking to eat acid or aversion to grease, nausea, morning sickness, etc., early pregnancy test paper combined with blood pregnancy test, ultrasound and other tests can be used to clarify whether it is an early pregnancy or not.