HCG, or human chorionic gonadotropin, can reach a peak of 50,000-100,000 U/L and is a commonly used clinical indicator to monitor the development of pregnancy. HCG production starts on the sixth day after ovulation, when the trophoblast layer of the fertilized egg is formed. HCG can be measured in peripheral blood about 1 day after fertilization, and rises 1-fold every 1.7-2 days, reaching 100 U/L on the 14th day after ovulation, and declines rapidly after reaching its peak in the 8th-10th week of pregnancy. In mid to late pregnancy, HCG is only 10% of its peak. HCG levels in urine and blood are close and have mild diurnal fluctuations, and are usually measured using the first urine or blood specimen in the morning. If the HCG value is low, it may be a sign of embryonic development that does not correspond to the last menstrual period and needs to be recalculated, or it may be a sign of poor embryonic development or even fetal arrest (abortion), which then leads to early miscarriage. Ectopic pregnancy should be suspected if measured at 2-3 days interval without exponential rise. At this time, the patient needs to ensure sufficient rest, and the HCG value can be rechecked again under the guidance of the doctor. If the HCG value is higher than normal, it indicates a possible abnormal pregnancy, such as gravidity, and the pregnant woman should immediately go to the hospital to improve other examinations, such as gynecological ultrasound, etc. When the HCG is at normal level, the pregnant woman need not worry too much, keep a good attitude and go to the hospital regularly for routine examinations to clarify the fetal growth and development.