What does placenta mean by posterior wall?

Placenta is located in the posterior wall, anterior wall, lateral wall and uterine bottom are the normal attachment position of placenta, placenta posterior wall refers to the attachment position of placenta in the posterior wall of uterus, is a description in medicine, is normal. If placenta previa, it is a relatively dangerous state, belonging to pathological pregnancy, can be divided into central placenta previa, partial placenta previa, marginal placenta previa, low placenta previa, normal late pregnancy or labor after showing no obvious incentives, painless repeated vaginal bleeding, bleeding volume will cause shock or even fetal death in utero.