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What does it mean to have a ‘posterior placenta’?

Did you know that the placenta can get attached to any part of the uterine wall? But does the position of the placenta really matter? Read on to learn what it means to have a posterior placenta and what it can tell you about your baby. 

What is the Placenta?

The placenta is an organ that supports fetal development during pregnancy. It’s where fetuses get nutrients and oxygen from, and it filters out waste from babies’ blood. Your baby is connected to the placenta through their umbilical cord. 

The location of the placenta is chosen early in pregnancy, when the fertilized egg attaches to the wall of the uterus. 

It can be located at the front of the uterus (anterior), the back (posterior), at the top (fundal), or the bottom (low-lying). 

Placental locations matter because the blood supply to the placenta will be different depending on where it is. This blood supply affects the growth and maturation of the fetus. 

The placenta can, in rare cases, be a physical barrier to birth. Let’s discuss why we care about placental locations in the first place.  

Why Does Placental Location Matter?

Like we said, how the placenta is positioned affects blood flow to the fetus. The anterior, posterior, fundal, and low-lying positions are all normal. There are risks associated with each location, just like there are risks in each pregnancy. 

The greatest risk is in the case of placenta previa. This means that the placenta is at the bottom of the uterus, blocking the birth canal.

This is rare, occurring in only about 1 in 200 pregnancies. A placenta previa location can be the difference between a vaginal or cesarean delivery for some women. 

Your obstetrician or midwife will closely monitor the location of your placenta throughout pregnancy and labor, to be sure it is not blocking the cervix. 

Placental location can also be an important indicator of pregnancy outcomes. Blood supply to the placenta, and hence the fetus, can change depending on where it is in the uterus. 

Different placental locations are associated with specific pregnancy risks, such as preterm labor and Small for Gestational Age (SGA) infants. 

 

What does it mean to have a posterior placenta?

posterior placenta

A posterior placenta means that your placenta is on the back wall of your uterus. This position is considered normal, but it does come with risks. 

The posterior placenta location is linked to a risk for preterm and still-birth. This could be because the back wall of the uterus has less blood supply.

The posterior wall is also longer and thicker, which could affect its ability to supply nutrients as it stretches throughout pregnancy. 

Posterior placental placement has also been linked to A-positive blood group, although we’re not sure why. 

Women with a posterior placenta may experience more back pain. This is because the placenta can push on the back of the uterus and the spine. Other factors like high BMI, large fetuses, and multiparous births also increase risk for back pain. 

This list may make you nervous if you know your placenta is posterior, but there are risks associated with the other ‘normal’ locations as well.

Anterior placentas are linked to a fetal developmental problem called Intra-uterine growth restriction (IUGR), as well as preeclampsia. 

Fundal placentas are associated with preterm labor and preeclampsia. 

Low-lying placentas have the risk of migrating to cover the cervix to obstruct labor.  

Remember that all pregnancies have risks. The posterior placental location has a relatively lower risk, and is a good location for easy birth. 

Placental location

Is it Normal to Have a Posterior Placenta?

Yes. 
A posterior placenta is a perfectly normal location, and could even help the fetus move down the birth canal during labor. 

Symptoms of a Posterior Placenta

A posterior placenta gives your baby more space to move around at the front of your uterus. Some women experience kicking and movements earlier during pregnancies with a posterior placenta. 

The posterior placenta location has been linked to more back pain for some women. This location may add pressure to the spine. You can try to reduce pressure on your back by lying on your side, or even crouching on all fours. 

Symptoms of a Posterior Placenta

A posterior placenta gives your baby more space to move around at the front of your uterus. Some women experience kicking and movements earlier during pregnancies with a posterior placenta. 

The posterior placenta location has been linked to more back pain for some women. This location may add pressure to the spine. You can try to reduce pressure on your back by lying on your side, or even crouching on all fours. 

How Can I Know Where My Placenta is?

When you get your first ultrasound, your medical provider will be able to tell you where your placenta is. This usually happens between 18 and 20 weeks. 

What are the Complications and Risks of a Posterior Placenta?

On its own, the posterior placenta does not pose any more risk than other placental locations. In fact, the posterior location has been associated with less risk than the other ‘normal’ locations. 

If a posterior placenta is low in the uterus, it could migrate further down to cover the cervix. This would become placenta previa, and could mean that a cesarean delivery is necessary. 

On the other hand, the posterior placenta can also embed too deeply in the uterus. This creates the opposite problem: placenta accreta. The placenta may attach itself in the muscles around the uterus, or even the uterine wall. This creates a risk in the third stage of labor, when the placenta comes out. In placenta accreta, there’s high risk for bleeding. Still, this is quite rare. 

So, here are the risks and complications that could be associated with posterior placenta:

  • Preterm labor
  • Still-birth
  • Back pain
  • Placenta previa
  • Placenta accreta

Does a posterior placenta mean a boy or a girl?

No. The best way to find out the gender of your baby is through ultrasound. Methods to predict gender are unproven and may be misleading. Trying to predict the gender of your baby can be fun, but remember that these guesses are not based on science or medicine. 

There is some evidence that placental location is associated with gender. One study showed that 73% of female infants had an anterior placenta, while only 28% of boys did

This has led a lot of people to think that posterior placentas mean boy babies. But these findings are small, and more research needs to determine if there is a true link between placenta placements and gender. 

Does the posterior placenta affect birth and labor?

Generally no.
For the most part, the posterior placenta location is perfect for birth. It allows the baby to move down in the birth canal during labor, and should easily come out during the third stage of labor. 

If a posterior placenta moves down to cover the cervix, this could be a problem for labor. This is called placenta previa, and it’s very rare. Your doctor or midwife will monitor the placement of your baby and your placenta to be sure both are safe for labor. 

Can I have a normal delivery with a posterior placenta?

Yes! The posterior placenta location can even help smooth labor, because the placenta is out of the way during delivery. 

The only times when a posterior placenta may interfere with labor is if it migrates down to block the cervix (placenta previa), or embeds too deeply in the uterine wall (placenta accreta). Still,  these are very rare and will not necessarily affect your pregnancy. 

When should I consult a doctor?

Your OBGYN will follow the location of your placenta throughout your pregnancy. If you have questions about the location of your placenta, as well as the risks, let them know. They should be happy to explain placental locations to you. 

If you are experiencing new abdominal pain or tenderness, vaginal bleeding, or unusual contractions, go to a doctor immediately. These symptoms can be associated with placental abruption, in which the placenta detaches from the uterine wall. This is rare but can be a big problem both for you and your baby. 

Summary:

  • Posterior placental placement is normal.
  • The posterior placenta is one of the least risky positions. However, every placental position comes with its own set of pros and cons.
  • If you have a low-lying placenta or a placenta that is deeply attached into the uterine wall, then your risk of complications is higher. 
  • Women with a posterior placenta may experience more kicking and back pain.
  • There is no evidence to support the theory that placenta placement is linked to gender. 

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