Common Positions of the Placenta in Pregnancy

The placenta is an important organ which grows in the uterus of a pregnant woman to supply oxygen and essential nutrients to the baby and to remove waste products from the baby’s blood. The placenta attaches to the wall of a pregnant woman’s uterus and is connected to the baby by the umbilical cord. During pregnancy, the placenta may attach itself at the top, side, front, or back of the uterus. In rare cases, it may even attach itself in the lower uterine region and block the cervix. In this article, we will discuss the common positions of the placenta during pregnancy and how they affect pregnancy.

After the delivery, it is usually expelled from the mother’s body, but it may not happen automatically always. When the placenta remains in the womb, it is called retained placenta.

What Are the Different Placental Locations?

The placenta, a large pancake-shaped organ, develops during pregnancy and attaches itself to the wall of the uterus. But it can attach itself in different positions. The different possible placental locations are mentioned below:

1. Posterior Placenta: Usually, a fertilized egg implants on the back of the uterine wall. In this case, the placenta also develops or grows on the back wall of the uterus. When the placenta is in this position, it is called the posterior placenta.

2. Anterior Placenta: When the fertilized egg attaches itself on the front side of the uterus, the placenta develops on the front wall of the womb and the baby grows behind it. When the placenta is at the front side of the uterus, it is known as the anterior placenta.

3. Fundal Placenta: When the placenta positions itself in the fundus or at top of the uterus, it is known as the fundal placenta. Sometimes, the placenta could be in a fundal-anterior position or fundal-posterior position. A fundal-anterior placenta is located usually at the top of the womb and extends slightly towards the front of the womb. A fundal-posterior placenta is also located at the top of the womb, but it extends towards the back of the womb.

4. Lateral Placenta: When the placenta implants to the lateral wall of the uterus, either on the right side of the womb or on the left side of the womb, it is called lateral placenta.

5. Placenta Praevia (Low-Lying Placenta): When the placenta grows towards the lower end of the uterus or towards the cervix, it is known as a low-lying placenta. If the placenta reaches the cervical opening partially or covers it completely, then this condition is known as placenta praevia and it can lead to many complications in pregnancy.

How Is the Location of the Placenta Determined?

The location of the placenta is determined by carrying out an ultrasound test. Getting an ultrasound done is safe and simple. If you are pregnant and want to know whether the position of the placenta is normal, you can get an ultrasound scan done. Most likely, your doctor will suggest it too. To determine the position of the placenta, the nurse will apply a water-based gel on your abdomen and pelvic area. Then she will place an instrument known as transducer on your belly. With the help of high-frequency ultrasound waves, the transducer will display the image of your uterus and the placenta on a screen. By conducting this scan, your doctor will understand if your placenta is placed normally or not.

Does the Position of the Placenta Change During Pregnancy?

The placenta occupies a large surface area in the uterus in the initial stages of pregnancy. The placenta can change its position during pregnancy. In the initial stages of pregnancy, the placenta may appear low lying but as the pregnancy progresses the placenta may migrate to the upper segment. This is called ‘placental migration’. In the case of placenta praevia, this placental migration is unlikely to occur.

What Are the Normal Positions of the Placenta During Pregnancy?

In terms of position, the placenta can position itself either on the front side of the uterus or at the backside of the uterus, depending on where the fertilized egg implants itself after going through the fallopian tube. The normal positions of the placenta are fundal, anterior, and posterior.

When Should You Worry?

If the placenta is in posterior, anterior, fundal, or lateral position, then it is not a problem. All these positions are normal for the placenta to attach itself and develop. However, if the placenta grows on the lower end of the uterus or towards the cervix of a woman, it can be a cause for concern. This condition, as explained above, is called placenta praevia, and it can cause bleeding due to premature detachment of the placenta. Placenta praevia may also restrict a normal, vaginal delivery as it blocks the cervix. A periodical ultrasound test is done during pregnancy to determine the position of the placenta so that the doctors know of any possible complications which may arise due to the position of the placenta.

Signs of  Placenta Praevia

One of the signs of placenta praevia could be sudden, painless vaginal bleeding. The other signs and symptoms of placenta previa include:

• Painless bleeding
• Bleeding after intercourse
• can occur as early as 20 weeks

If you are pregnant and notice that any of these symptoms, it can be indicative of a low-lying placenta. You should immediately consult your doctor in such a situation.

What Are the Causes of a Low-Lying Placenta?

While the exact reason or cause of a low-lying placenta is not known, this problem is commonly seen in women who are older, have undergone a C-section delivery before, who smoke, or have scars inside the uterus. Women who have suffered from placenta praevia during a previous delivery are also at an increased risk of a low-lying placenta. In case you have had a low-lying placenta during a previous delivery, you should inform the same to your doctor well in advance.

How Low Is Too Low?

Under normal circumstances, the placenta will not be low-lying during birth if the distance between the placenta and the cervix is more than 2 centimetres in the 18-20th week of the pregnancy. If the distance between the two is less than 2 centimetres during the 18-20th week, it may remain low at the time of birth. Your doctor might ask to get the position of placenta re-checked in the third trimester to determine its position before the delivery.

What Happens If the Placenta Is Too Close to the Cervix?

If the placenta is too close to the cervix, the mother-to-be will be diagnosed with placenta praevia. The risks of this condition include premature labour. If the placenta detaches prematurely, it can cause bleeding. Placenta praevia can also make a vaginal delivery difficult.

The position of placenta plays an important role in ensuring the smooth and safe delivery of the baby. A low-lying placenta or placenta praevia is the only situation where it can cause trouble at the time of labour. Since the reason for a low-lying placenta is not known, it is difficult to prevent it from happening. However, with the help of sonography and ultrasound, the doctors can be aware of the placenta position in advance and suggest necessary precautionary steps for safe delivery.