When a woman is pregnant, an organ called the placenta delivers nutrients and oxygen from the blood of the mother to the blood of the baby. The placenta covers a wide area and is connected to the uterus of the mother. The umbilical cord connects the placenta to the baby.

The front area of the uterus is considered the anterior; the back side is the posterior; the fundal is the top wall; and the sides of the uterus are the right and left laterals. It doesn’t matter which area of the uterus the placenta situates itself, but if the lower portion is too far down it can make it difficult for the baby’s head to descend when it is time for the birth. Having a posterior placenta means that it can cause the mother to experience excessive bleeding while pregnant as well as while giving birth.

What Is Posterior Placenta?

The uterus positions itself among the pelvic bones of the mother. When the placenta of a mother attaches itself to her uterus on the back wall, it is considered a posterior placenta. This area of the uterus is right near the spinal column of the mother. When the egg is fertilized, it remains close to that area of the uterus and grows from there. The “posterior” represents the back and the “anterior” means the front.

Is Posterior Placenta Normal?

As the baby begins to grow, so does the uterus. Both an anterior and posterior are normal for both the baby and the mother. When it is in the vertical location of the uterus, this makes it a placenta posterior. When the placenta is on the back wall towards the upper portion of the uterus, it is considered the placenta posterior fundal. This is considered the best location for the baby to be in as it allows the baby to move into the anterior position just before it is born. While it faces its mother’s spine, the crown of the infant’s head is able to make its way towards the birth canal.

How Does the Placental Position Change?

When a woman is pregnant, an ultrasound is implemented to find out exactly where the placenta is and what its location to the cervix is. It is normal for the placenta to change throughout the pregnancy. Midway through the pregnancy, the placenta takes up 50% of the space on the surface of the uterus. At the 40 week mark, the placenta only takes up from 17 to 25% of the surface of the uterus. It’s not that the placenta is shrinking; it’s that it grows more at different times of the pregnancy.

By the third portion of the pregnancy, the head of the baby begins to prepare for labor by descending down to the pelvic area. The lower portion of the uterus begins to thin out from the pressure that the baby’s head is putting on it. This is when the placental attachment looks like it is beginning to rise.

When to Worry About Placental Position

When the placenta grows in the direction of the cervix, it is called placenta previa and it could be a cause for concern. The placenta has a chance of detaching itself from the unstable portion of the cervix towards the lower portion of the uterus. This could cause premature labor and complications as a result of heavy bleeding.

Usually there is nothing to worry about if a scan that is taken in the beginning of your pregnancy determines that your placenta is located at the bottom of your uterus. The placenta will be moving upwards as the pregnancy advances. Nor should you worry about posterior placenta. 

Later on in the pregnancy this position of the placenta could cause problems. Placenta previa means that the cervix has become obstructed and the baby may not be able to be born vaginally. Placental abruption occurs when the uterine wall is stretched towards the second half of the pregnancy resulting in excessive bleeding. It is important to keep an eye on the location of the placenta throughout the pregnancy to determine if the mother will be able to deliver her baby vaginally or if she will require a Caesarian section.