Definition - What does Posterior Placenta mean?
A posterior placenta is a placenta that attaches to the back of the uterus, close to the spine (posterior means back). Having a posterior placenta is normal as it doesn’t affect the nutrition and growth of the developing baby in any way.
FertilitySmarts explains Posterior Placenta
The ideal location of the placenta is fundal, i.e., it attaches to the top of the uterus. With that said, the fertilized egg may sometimes attach itself at the back of the uterus. The placenta then starts growing on the back wall of the uterus and is known as a posterior placenta.
Having a posterior placenta doesn’t mean that the location of the said organ is abnormal. In fact, this position of the placenta doesn’t matter when it comes down to the baby’s nutrition and growth. On the contrary, a posterior placenta offers an added advantage over the anterior placenta. Having the placenta on the back allows the woman to start feeling the baby’s movements and kicks early on during the pregnancy. Moreover, a posterior placenta is one of the ideal placental positions as it allows the baby to descend into the birth canal easily and align itself for a vaginal birth.
Because of this, an ultrasound study showing a posterior placenta is normal. However, a posterior placenta is shown to be associated with premature labor and delivery. This may be because of the structure of the back of the wall of the uterus, which somehow lessens the efficiency of the placenta attached to that wall. The blood supply to the uterus is uneven, causing the back wall of the pregnant uterus to be longer and somewhat thicker. All these factors may impact uterine blood supply, in particular when the uterus enlarges to accommodate the pregnancy. Therefore, it's important to monitor a pregnant woman with a posterior placenta.
Moreover, the placenta can migrate and change its position anytime during pregnancy. Only if the placenta grows downward and reaches too close to the lower portion of the uterus called cervix (a condition called placenta previa), will it interfere with the baby’s descent during delivery, warranting emergency C-section. Ultrasound is typically done in all pregnancies on a timely basis to determine any changes in the position of the placenta and its relation to the cervix.