使胎儿能在子宫内长期生存和发育的条件,是由妊娠期母体的免疫耐受性、胎盘的组织生理学综合特性和胎儿的免疫活性所决定的。随着胚胎、胎儿各种器官及组织的发生和分化,母体、临时性器官和胚胎之间的结构上的相互关系也发生变化,而这种关系决 The conditions that allow the fetus to survive and develop in the uterus for a long time are determined by the immune tolerance of the mother during pregnancy, the general physiology of the placenta, and the immunocompetence of the fetus. With the embryonic, fetal organs and tissues of the occurrence and differentiation, the mother, the temporary organ and embryonic structure between the relationship also changes, and this relationship