Posterior placenta: what it means for your pregnancy
Wondering how the position of your placenta can affect your pregnancy, birth and baby? Here's everything you need to know about posterior placentas and what to do if you're told you have one.
Placentas are pretty amazing – a temporary yet complex life-giving organ that grows out of the fertilised ovum and attaches to your uterus, providing oxygen and nutrients to the developing baby via the umbilical cord.
There's no other organ in the body quite like it! However, placentas can come in all shapes, sizes and positions and depending on where yours is located, you may have a different experience of pregnancy and birth.
So, what exactly does it mean if you're told you've got a posterior placenta, and should it be any cause for concern?
We spoke to NHS GP Dr Philippa Kaye to find out everything you need to know about posterior placentas, including any risks or benefits of a posterior placenta position, to what it means when it comes to delivering your baby.
What Is a Posterior Placenta?
"The placenta forms in the womb during pregnancy, it delivers oxygen and glucose to the baby from the mother via the umbilical cord and removes carbon dioxide from the baby," says Dr Philippa Kaye.
"The placenta can form in any part of the uterus and can move upwards as the uterus grows and develops, up until about week 32 of pregnancy.
"In a posterior placenta, the placenta forms on the back of the uterus, on the back wall, while in an anterior placenta, it grows on the front wall. In a posterior placenta, the placenta is between the baby and the mother’s back. These are both normal positions for the placenta to form.
Other common positions for the placenta are fundal (when the placenta is at the top of the womb) and lateral (when the placenta is on the right or left side of the womb).
The fundal placenta position is often thought to be the most ideal position for a placenta because it allows for maximum blood flow to the baby and means it's easy to see baby during scans and to monitor the heartbeat using a doppler.
However, if you have a posterior, anterior or lateral placenta position, there's no cause for concern as these are common positions too.
You could also be told you have a low-lying placenta or placenta previa, which means the placenta is located towards the bottom of your uterus and may be obstructing your cervix, making vaginal delivery difficult.
If you have placenta previa, you will be given extra scans and be closely monitored until your due date. Placenta previa may result in a planned C-section.
Symptoms of a Posterior Placenta
"With a posterior placenta, as the placenta is on the back of the womb, the space for the baby to move around, stretch and kick will be at the front, meaning that you might notice the foetal movements earlier in the pregnancy than in women with the placenta at a different point in the uterus," says Dr Philippa Kaye. "It can also make it easier to get good views of the baby during ultrasound scans!"
Another benefit to having a posterior placenta is that your baby will have plenty of space at the final stage of pregnancy to move into the optimum position for a vaginal birth.
You may be told what position your placenta is in at your 12 week scan and/or 20 weeks scan. However, if you're not told anything, don't worry, because that probably just means there's no cause for concern and your placenta is behaving as it should be.
How a Posterior Placenta Affects Pregnancy
"Having a placenta in a posterior position should not affect the development of the baby in a negative way," says Dr Philippa.
"There can be issues with the placenta, for example, placenta accreta, where the placenta attaches too deeply into the uterus which can lead to bleeding in labour. However, there isn’t an increased risk of placenta accreta with a placenta in the posterior or anterior position."
The only way having a posterior placenta may affect your pregnancy is that you may feel your baby moving earlier in the pregnancy than other women, and healthcare professionals should find it easy to perform ultrasound scans and find the baby's heartbeat during examinations.
Differences Between Posterior and Anterior Placenta
The main difference between a posterior placenta and an anterior placenta is the position of the placenta in the womb.
A posterior placenta is located on the back wall of the womb (nearest to the mother's spinal cord), while the anterior placenta is located on the front wall of the uterus (nearest the mother's belly button).
Neither an anterior placenta nor a posterior placenta is considered better than the other, as they are both normal positions.
Other differences between posterior and anterior placentas include how early or how strongly a mother feels her baby's movements (anecdotal evidence suggests mothers feel their baby "kick" earlier with a posterior placenta) and how clearly you can see baby during an ultrasound scan. With a posterior placenta, you may get a clearer view of the foetus than you would with an anterior placenta.
Can a Posterior Placenta Affect Labour and Delivery?
"If the placenta is in the posterior position but high in the uterus, then it is unlikely to cause an issue in labour and delivery, there is room in front for the baby to move down to the birth canal and out," says Dr Philippa.
"However, if the placenta is in a very low position, very near or over the cervix, whether or not it is in an anterior or posterior position, it can lead to bleeding, before or during labour and can lead to preterm labour."
Does a Posterior Placenta Reveal the Baby’s Sex?
Some people believe that the position of the placenta is linked to the baby's gender. However, there's no scientific evidence to support this at all, and the position of the placenta is pure chance, depending on where the fertilised egg implants in your womb.
Remember, placentas also move throughout the pregnancy, so it would be highly unlikely that they have anything to do with baby's sex. In fact, in 9 out of every 10 women, the placenta will be in the upper part of the womb by around 32 weeks of pregnancy.
If you do love a baby sex theory, though and want to have some fun, the myths around baby's sex and placenta position are called the Ramzi Theory or Ramzi Method. This theory suggests that you can tell the sex of your baby from an early ultrasound scan (from 6 to 12 weeks) based on whether the placenta is on the left or right side of the uterus.
If your placenta is on the right, goes the theory, you're having a boy; if your placenta's on the left, you're having a girl.
However, it can be tricky to see the placenta with an untrained eye by looking at your scan pictures, and scans are often mirror images of the womb, so working out the side can be difficult unless you ask your sonographer.
Remember, this is just a bit of fun, and one of many gender prediction theories out there, as there's no scientific evidence to support the theory.
When to seek medical advice
Complications of the placenta aren't common, however, there are times when you may need to seek medical advice. If you have a low-lying placenta and experience painless, bright red bleeding from the vagina you should contact your midwife or GP immediately.
In rare cases, some women experience placental abruption, a serious condition in which the placenta starts to come away from the inside of the womb wall. Symptoms of placental abruption include stomach pain, bleeding from the vaginal and contractions. If you experience any of these symptoms, you should speak to your midwife, doctor or call 111 immediately, as your baby may need to be delivered straight away.
You should also seek medical advice if you experience any abdominal trauma while pregnant (for example, a car accident or a fall), and any bleeding, pelvic pain or cramping during pregnancy is also a cause for concern and should be reported to your healthcare provider. As always, if you are concerned or worried about anything, however minor, when pregnant, it's best to speak to seek medical advice.
About our expert: Dr Philippa Kaye
Dr Philippa Kaye works as a GP in both NHS and private practice. She attended Downing College, Cambridge, then took medical studies at Guy’s, King’s and St Thomas’s medical schools in London, training in paediatrics, gynaecology, care of the elderly, acute medicine, psychiatry and general practice.
Pics: Getty Images