Generally pregnant women are divided into early, middle and late pregnancy, pregnancy is counted from the last day of menstruation, let’s say I got my period on the 1st, then it is counted from the 1st, counting the weeks of pregnancy. We generally call it early pregnancy until 13+6 weeks, then between 20-24 weeks of pregnancy, it’s called mid pregnancy, and then after 28 weeks it’s called late pregnancy. Early pregnancy is the stage of fetal differentiation and development, which is susceptible to external factors and maternal illnesses leading to fetal malformation or miscarriage. Prenatal ultrasound examination at this time in the middle pregnancy is mainly to carry out a comprehensive and integrated examination of the digestive system, cardiovascular system, genitourinary system, nervous system and musculoskeletal system of the fetus, and various organs. In late pregnancy, the fetus becomes more mature, gains weight rapidly, asks for more nutrients from the mother, and stores them in the body for consumption after birth.