The left posterior wall of the placenta is a description of where the placenta attaches. The location of placenta attachment in the uterine cavity is not exactly the same from one pregnancy to another and may be in the anterior, lateral or posterior wall, or at the base of the uterus. Regardless of the position of attachment, it is normal as long as it is not placenta praevia. The normal position of placental attachment has no effect on the normal endocrine function of the placenta, or on the ability to exchange substances, and does not affect fetal development differently. During the ultrasound examination, it is necessary to observe, whether the placental parenchymal echo is abnormal. If the placenta has obvious large blood sinus formation, or large calcification, it will reduce the function of the placenta and affect the normal development of the fetus. If the position of the placenta is too low, it will also have a negative impact on the development of the fetus and needs to be taken seriously.