In most cases, an HCG value of 1800 IU/L belongs to 4-5 weeks of pregnancy, but the number of weeks of pregnancy cannot be accurately deduced based on the blood HCG value alone, and should be combined with the results of estrogen, progesterone and ultrasound to make a comprehensive judgment. There are many clinical methods to calculate the pregnancy time, for women with regular menstruation, it can be calculated according to the time of the last menstruation; if you have irregular menstruation or forget the time of the last menstruation, you can only calculate the pregnancy time by ultrasound examination of the development of the gestational sac; later on, you can also calculate the pregnancy time by the length of the fetal biparietal diameter. There may be a difference between the number of weeks of pregnancy and the number of days of menopause, but it is normal for the difference to be within 1-2 weeks. Since the length of menstrual cycle and the early and late conception of each person are different, there may be some error in the week of pregnancy. In early pregnancy, women need to go to the hospital as soon as possible to improve blood HCG, estrogen, progesterone and ultrasound tests to help estimate the gestational week and keep abreast of the embryonic development. If the embryo is stunted or has stopped developing in early pregnancy, the pregnancy should be terminated as soon as possible.