What is posterior placenta?

The placenta takes away waste products from your baby’s blood (such as carbon dioxide). The growth of your baby depends on the quality and effectiveness of your placenta, so it has a huge role to play in pregnancy. The placenta is fully formed and functioning 10 weeks after fertilization and is approximately 20cm in diameter, 2.5cm thick, and weighs one-sixth of your baby’s weight (at term). It attaches to the wall of your uterus. Its position can be anywhere — front, back, right, or left. If the placenta attaches to the back of the uterus, it's known as a posterior placenta. 

In the initial weeks of pregnancy, the fertilized egg (blastocyst) travels through the fallopian tubes into the body of the uterus.

This fertilized egg can implant itself anywhere on the wall of the uterus. The spot where it attaches is known as the placental location.

When the placenta attaches to the posterior wall of the uterus, it is categorized as a ‘posterior placenta’.

The Journey of the Placenta

The following are the stages of the placenta's development:

1. The placenta starts taking shape very early when the blastocyst implants itself into the uterus, which is right after conception.
2. The blastocyst then develops into the embryo.
3. The outer cluster of cells which is called trophoblast begins to gradually form the placenta.
4. The trophoblast is characterized by quick growth and its cells split into two. Trophoblast cells divide into cytotrophoblasts and syncytiotrophoblasts.
5. The cells positioned in the inner placenta reshape blood vessels in the uterus. This is how they are able to provide nutrients to the fetus.

Studies have also shown an association of placental position with the mother’s sleep position, blood pressure, and blood type.

What Are some facts about Posterior Placenta?

The blood flow through the uterus is not uniform, so the blood supply to the baby does depend on the position of the placenta. When the placenta is attached in the more normal places (anterior, posterior, fundal, or lateral) there are rarely any complications due to bloody supply. However, if the placenta is located at the bottom of your uterus (called placenta previa), there can be more complications to consider for both the mum and baby.

There is no risk associated with a posterior placental position unless it is very low and covers the cervix.

Also, the location of your placenta can change as your pregnancy progresses. Doctors use ultrasound to determine where the placenta is located and to monitor its movement during your pregnancy. The position of the placenta can be seen as early as 10 weeks’ gestation, where it looks like a thickened rim of tissue around the womb.

About 10-15% of placentas are considered low-lying at the 18-20 week ultrasound but only 0.5% are still low-lying at term.

When the posterior placenta wholly or partially covers the cervix, it could give rise to some complications.

Posterior placenta offers baby a smooth exit in a vaginal delivery.

Mums-to-be with posterior placenta have lesser chances of back pain than those with anterior placenta.

Mums-to-be may feel stronger motions, movements, and kicks of the baby early on during the pregnancy if they have a posterior placenta.

5 Myths to Know About Posterior Placenta

The posterior placenta is the best possible position

There is no ideal placental position as such, so none can be rated ‘best’ or ‘worst’. This position, is however, one of the normal positions and does not carry risks.

The posterior placenta can heighten the risk of a C-section

Not true. You can have a normal delivery with a posterior placenta.

The posterior placenta increases the risk of preterm deliveries

Many certified bodies have reviewed this, and there is no proof.

Posterior placenta means it's a boy

This theory is not proven scientifically. Although research statistics indicate the relationship between the sex of the baby and placental position.

Summing Up... Posterior Placenta

A posterior placenta is a placenta position wherein the placenta attaches itself to the back of the uterus. Numerous people speculate that a posterior placenta means that you are having a boy. However, this theory is not scientifically proven. What is scientifically proven? If the bottom part of the placenta is too close to the cervix, it may cause complications when the baby's head descends during labour. Otherwise, a posterior placenta is a normal placenta position and vaginal birth can be possible with it.

The doctor will keep monitoring if it's low - often it travels upwards on its own.