The second trimester is the end of the 12th-27th week of pregnancy, when the fetus grows faster, on average about 1.6 cm per week during the 20th-24th weeks. The entire cycle of pregnancy is 280 days, or 40 weeks. For women with regular menstrual cycles, the first day of the last menstrual period can be used to calculate the time of pregnancy. Clinically, the entire period of pregnancy is divided into early, middle and late stages. Among them, early pregnancy is defined as before 12 weeks of pregnancy, middle pregnancy is defined as the end of 12-27 weeks of pregnancy and late pregnancy is defined as ≥ 28 weeks of pregnancy. The fetal movement can be felt at around 20 weeks of mid-pregnancy, and the fetal heart sounds can be heard through the abdominal wall of the pregnant woman with an ordinary stethoscope at around 18-20 weeks of pregnancy. In the middle of pregnancy, it is recommended to have an obstetric checkup every 4 weeks, during which Down’s syndrome screening, macrosomia screening, glucose tolerance screening, etc. can be performed. Pregnant women should pay attention to proper activities, eat more fresh fruits and vegetables, and eat less spicy and stimulating food.