The placenta is part of the fetal membranes and is an important organ for material exchange between the fetus and the mother, consisting of amniotic membrane, lobulated chorionic membrane and basal metaplasia, shaped like a flat disk. The diameter of full-term placenta is about 16-20cm, thickness is about 0.5-3.0cm, weight is about 500g, and it is divided into two parts: maternal side and fetal side. The maternal side is the side of the basal meconium peeling off from the uterine wall, with dark red color and rough surface, divided into 15-20 lobules by shallow grooves. The fetal side is grayish white, smooth and flat, covered with amniotic membrane, the umbilical cord is attached to it, and there are umbilical arteries and veins dissipating in all directions from the attachment point. The placenta is spongy and consists of villi and blood sinusoids. The villi are 1.0-1.5 cm long and extend into the blood sinusoids between the chorion and the basement membrane like dendrites.