Normally, pregnancy lasts for 40 weeks and 10 gestational months, i.e., from the first day of the last menstrual period, and the day of 40 weeks of pregnancy is the expected date of delivery. Pregnancy is mainly the period of time from the fertilization of a mature egg to the expulsion of the fetus and its appendages, and is divided into early, mid and late pregnancy. The first trimester is before 14 weeks of pregnancy, the second trimester is from 14 weeks to 28 weeks of pregnancy, and the second trimester is after 28 weeks of pregnancy. With the increase of gestational weeks, the fetus grows and develops in the mother’s body, and it is normal to deliver between 37 weeks and 42 weeks of pregnancy. 37 weeks of pregnancy is full term, and the fetus is basically mature and can wait for contractions to start natural delivery at any time. If a fetus is born between 28-37 weeks, it is preterm, and its survival rate is relatively low, requiring hospitalization. If the baby is born between 28 and 37 weeks, it is considered premature and has a relatively low survival rate. Regular checkups are needed during pregnancy to understand the development of the fetus.