Introduction to the whole process of fetal development during pregnancy. Pregnancy is the process of the baby growing in the mother\’s body, and the development process of the fetus is also an extremely complex and wonderful process. During this process, the fetus gradually develops from a fertilized egg into a healthy baby. In this article, we will elaborate on what the baby goes through during pregnancy from four aspects. The embryonic period is the first 8 weeks of pregnancy, during which the embryo develops rapidly. After the fertilized egg hatches,