The blood test to check for pregnancy focuses on the value of human chorionic gonadotropin (β-HCG) and the trend of that value. Human chorionic gonadotropin generally exceeds 5 IU/L indicating a possible pregnancy and gradually rises and peaks around 8 to 10 weeks and then gradually declines, but is still above normal. In normal pregnancy, HCG is produced when the fertilized egg is deposited, i.e., when the trophoblast layer of the fertilized egg is formed on the 6th day after ovulation, and peripheral blood HCG can be detected about 1 day later, and then it rises by 1 times every 1.7-2 days, and it reaches about 100U/L on the 14th day after ovulation, and reaches a peak of 50,000-10,000,0000100U/L at the end of 8-10 weeks of gestation, and then it declines rapidly thereafter. In the middle and late stages of pregnancy, HCG is only 10% of its peak. At 6-8 weeks of gestation, HCG should increase at a rate of 66% per day, and if the rate of increase is less than 66% in 48 hours, it suggests a poor prognosis for the pregnancy. If HCG remains low and does not rise exponentially when measured 2-3 days apart, ectopic pregnancy should be suspected.