Detailed pictures of the entire fetal development process In the mother\’s body, the growth of the fetus from fertilized egg to birth is a very magical and wonderful process. The following will introduce in detail the different stages of fetal development, fetal organs, placenta, amniotic fluid and fetal respiration. Stages of Fetal Development Fetal development can be divided into three stages: early stage, middle stage and late stage. In the early stage, the fertilized egg undergoes division and cell differentiation to form a small ball composed of cells, which then enters the uterus.