Abstract: Recurrent spontaneous abortion is a common complications of pregnancy, which etiology and pathogenesis has not been fully elucidated. Sufficient uteroplacental blood flow is crucial for normal pregnancy, which depends on the maternal-fetal blood circulation system of high flow / low resistance resulted from physiologic transformation of the spiral arteries widespread throughout the placenta. Uterine spiral artery blood flow provides plenty of placental blood flow and nutrient to meet the development of embryos. The invasion extravillous trophoblast and apoptosis of uterine spiral artery cells are two key processes in the remodeling of the uterine spiral arteries. Failure of physiologic transformation of the spiral arteries will limit maternal blood flow into the placenta and the embryo therefore develops in a low blood flow / oxygen environment, which may lead to a series of pathological pregnancies. Early research has shown that decidual tissue of patients with recurrent spontaneous abortion were lack of trophoblast invasion, and performance the failure of physiologic transformation of the spiral arteries.

Key words: Recurrence, Abortion, habitual, Uterus, Placenta, Extravillous trophoblast, Trophoblasts；, Apoptosis