The HCG doubling pattern is a more than 1-fold increase in HCG at 72h intervals in early pregnancy. HCG is a glycoprotein hormone composed of α and β subunits, and the trophoblast cells start to secrete a small amount of HCG from the 6th day after fertilization, and it can be detected in maternal serum after the 10th day. In the middle and late stages of pregnancy, it may be only 1/10 of the peak value; finally, it disappears within 2 weeks after delivery. In early pregnancy, if HCG appears to double, it indicates that growth and development are relatively regular and not abnormal. In general, a gestational sac should be visible in the uterine cavity if the HCG value is greater than 2000 U/L. A yolk sac can be seen in the uterine cavity if the HCG value is greater than 10000 U/L. If no yolk sac is seen, it indicates a poor prognosis of the embryo. For twin pregnancies, the doubling of HCG will be more obvious because the release of HCG in the body is significantly increased in pregnant women carrying twins. In addition, in case of gravidity, HCG will also be significantly elevated and needs to be determined by ultrasound and once diagnosed, the uterus needs to be cleared as soon as possible. If HCG fails to reach doubling increase every other day, the pregnant woman needs to exclude the possibility of embryonic dysplasia or ectopic pregnancy. Also taking diuretics has the potential for false negatives. If pregnancy is confirmed, progesterone and estradiol are also indicators of pregnancy that need to be taken seriously. If a progressive decrease in progesterone levels and estradiol levels is found, it suggests a risk of miscarriage and should be supplemented promptly under the guidance of a physician. In addition, false positives may occur if the patient is taking anticonvulsants, hypnotics, etc.