In most cases, HCG value of 1800IU/L is 4-5 weeks of pregnancy, but only based on the blood HCG value can not accurately deduce the number of weeks of pregnancy, we need to combine the results of estrogen, progesterone and ultrasound to make a comprehensive judgment. Clinically, there are many ways to calculate the time of pregnancy, for women who have regular menstruation, it can be estimated according to the time of the last menstruation; if the menstruation is not regular, or if the time of the last menstruation is forgotten, then the time of pregnancy can only be estimated through ultrasound examination of the development of the gestational sac; in the later stage, it can also be estimated through the length of the biparietal diameter of the fetus, and the week of pregnancy shown in the ultrasound results may be different from that calculated from the number of days after the cessation of menses, generally the difference is within 1 week, and it may not be the same. There may be a difference between the number of weeks of pregnancy shown on the ultrasound and the number of weeks of pregnancy estimated from the days of menopause. As the length of the menstrual cycle varies in each person, and the time of conception varies, there may be some errors in the weeks of pregnancy, but as long as the growth and development indicators of the fetus are normal, there is generally no special effect. In early pregnancy, women need to go to the hospital as early as possible to improve the blood HCG, estrogen, progesterone and ultrasound tests to help estimate the gestation week and keep abreast of the embryo development. If the embryo develops poorly or stops developing in early pregnancy, the pregnancy should be terminated as soon as possible.