Placenta accreta – Types, Causes, Symptoms and Treatment

Definition

Placenta accreta, abnormal adherence of the placenta to the wall of the uterus, so that it remains in the uterus after the baby has been delivered. Although uncommon, placenta accreta poses serious dangers to the mother. If complicated by coexisting placenta praevia (development of the placenta in an abnormally low position near the cervix), severe bleeding before labour is common. If placenta accreta arises on the site of a scar from a former cesarean section, the uterus may rupture during labour. Otherwise, depending on the firmness with which the placenta is anchored, it may be removed manually after the baby is placenta delivered. If such removal is unsuccessful, an immediate total hysterectomy is usually indicated.

Epidemiology

Once a rare occurrence, placenta accreta is becoming an increasingly common complication of pregnancy, likely related to the increasing rate of cesarean delivery over the last five decades. Placenta accreta occurs in approximately 1:1000 deliveries with a reported range from 0.04% rising up to 0.9%. Differences in definition and study population may account for this wide range.        

Types of Placenta accreta

There are three types of this condition. The type is determined by how deeply the placenta is attached to the uterus.

Placenta accreta: The placenta firmly attaches to the wall of the uterus. It does not pass through the wall of the uterus or impact the muscles of the uterus. This is the most common type of the condition.

Placenta increta: This type of the condition sees the placenta more deeply imbedded in the wall of the uterus. It still does not pass through the wall, but is firmly attached to the muscle of the uterus.

Placenta percreta: The most severe of the types, placenta percreta happens when the placenta passes through the wall of the uterus. The placenta might grow through the uterus and impact other organs, such as the bladder or intestines.

Risk factors

Several factors are thought to increase a woman’s risk of developing placenta accreta. These include:

• Past uterine surgery (or surgeries), such as a cesarean delivery or surgery to remove uterine fibroids
• Placenta previa, a condition that causes the placenta to partially or fully cover the cervix
• A placenta located in the lower part of the uterus
• Being over the age of 35
• Past childbirth
• Uterine abnormalities, such as scarring or uterine fibroids

Causes of Placenta accreta

Placenta accreta is thought to be caused by scarring or other abnormalities with the lining of the uterus. These abnormalities may occur after procedures like C-section or fibroid removal.

Several risk factors may increase your risk of placenta accreta, including:

Previous C-sections (Cesarean sections): Women who have had multiple C-sections are at a higher risk of developing placenta accreta.

Placenta previa: Placenta previa is a condition where the placenta blocks the opening of the cervix. If you have placenta previa and have had C-sections, the risk for placenta accreta increases.

History of fibroid removal: If you have had a fibroid (non-cancerous growth or tumor) removed from your uterine muscle, the scarring could lead to placenta accreta.

Maternal age: Women older than 35 are more likely to have placenta accreta.

​Previous childbirth: The more pregnancies you’ve had, the higher your risk for placenta accreta.

Symptoms of Placenta accreta

Placenta accreta symptoms during pregnancy: (What the mother will experience)

No symptoms: Though this abnormality develops in the early pregnancy itself it does not cause any trouble until the time of delivery as the placental function is very much normal. Even if associated with placenta praevia (wherein the placenta is partly or completely inserted in the lower uterine wall) there is a 21.7% chance of no bleeding at any time.

Vaginal bleeding: If you have placenta praevia you may experience vaginal bleeding in the third trimester. The first bleeding episode may occur prior to 30 weeks (33.7% chance) or after 30 weeks (44.6% chance) or not at all (21.7%).

Preterm delivery: Not placenta accreta per se but if associated with placenta praevia, there is a 44% chance of delivering before 37 weeks.

So, if you experience vaginal bleeding or pain and contractions of the uterus in the third trimester it is important to meet your healthcare provider.

Placenta accreta Signs: (What the doctor will note)

If not diagnosed before delivery of the baby, the placenta accreta will present as:

Delay in the delivery of the placenta: Normally the placenta spontaneously separates and is delivered within 30 min of the delivery. In placenta accreta the placenta fails to deliver spontaneously and this will ring a bell to the doctor of the possibility of placenta accreta.

Profuse vaginal bleeding: The doctor will notice that there is more than normal vaginal bleeding, particularly when a manual separation of the placenta is attempted.

Soft uterus: Normally, after the baby is delivered, the uterus begins to become hard. This also compresses the blood vessels and stops bleeding. In placenta accreta due to the retained placenta, the uterus remains soft and as a result, the bleeding continues.

Reduced blood pressure and an increase in the pulse rate: This occurs when there is excessive blood loss.

Complications

• Damage to local organs (e.g., bowel, bladder, uterus and neurovascular structures in the retroperitoneum and lateral pelvic sidewalls from placental implantation and its removal
• Postoperative bleeding requiring repeated surgery
• Amniotic fluid embolism
• Complications (such as dilutional coagulopathy, consumptive coagulopathy, acute transfusion reactions, transfusion-associated lung injury, acute respiratory distress syndrome, and electrolyte abnormalities) caused by transfusion of large volumes of blood products, crystalloids, and other volume expanders
• Postoperative thromboembolism, infection, multisystem organ failure, and maternal death

Diagnosis and test

Placenta accreta is usually identified (seen) on ultrasound. The features can often be seen on your 20 week ultrasound scan. During every pregnancy scan the sonographer, or doctor, looks carefully at the placenta. They look especially closely if you:

• Have a low-lying placenta
• Had a previous caesarean
• Have vaginal bleeding after the early months of pregnancy

While most placenta accretas are seen on ultrasound, a few may not be. This is because some cases are subtle and difficult to see (we call this a ‘false negative’ result).

The opposite difficulty can also occur – sometimes the sonographer or doctor thinks the placenta is probably an accreta but it turns out not to be (we call this a ‘false positive’ result).

Your obstetrician may decide an MRI (magnetic resonance imaging) is needed to help sort out the diagnosis. However, MRI is also not 100% accurate. Sometimes it simply isn’t possible to be sure if the placenta is stuck or not until the time of birth.

Treatment and medications

Placenta accreta is a very serious, potentially life-threatening complication that needs appropriate treatment. Luckily, we now have the technology and surgical advances to keep both you and your baby safe during delivery, which almost always includes a c-section birth.

Cesarean Section

If you are diagnosed with placenta accreta before delivery, you will be advised to have a scheduled cesarean delivery. While the date chosen will balance your baby’s health with your health, this is often as early as 34 to 36 weeks gestation.

This means that treatment with steroids may be needed to mature your baby’s lungs before a preterm delivery. Some preterm infants will need care in a neonatal intensive care unit (NICU).

High-Risk Care

Once diagnosed, talk to your doctor about their expertise with PAS and whether or not they are the best person to manage your care. If they are not highly experienced in treating placenta accreta, they will likely refer you to a specialist who is. You can also decide to switch to a more experienced physician if you have any qualms about your current doctor’s qualifications.

Additionally, you may need to reconfigure your birth plan, including where you deliver. Ideally, deliver at a tertiary care level hospital that is equipped to handle this type of complex surgical birth.

Bigger, well-equipped hospitals offer the best chance for the healthiest outcome, as they have more expertise, highly trained specialists, and access to top-of-the-line equipment, and they handle more of these cases.

Blood Transfusions

Sometimes, massive hemorrhages occur before, during, and/or after delivery, requiring blood transfusions. Over 90% of mothers with placenta accreta require a blood transfusion, so planning ahead and coordinating with the hospital staff and blood bank are important steps. Sometimes, you can ask your doctor about banking blood prior to delivery specifically for your use.

Hysterectomy

An often upsetting truth about treating PAS is that you may lose your uterus in the process of successfully managing your care. In fact, many studies show that the best outcomes include planning ahead to do a cesarean hysterectomy.

This means that after the birth of the baby via cesarean section, the uterus is removed rather than trying to remove the placenta from the uterus and risk incurring even more bleeding and damage.

In isolated cases, when the mother hopes to retain fertility, new procedures are emerging that may successfully save the uterus. However, this option is not recommended or possible for most women.

Prevention of Placenta accreta

Placenta accreta cannot be prevented. The risk of placenta accreta goes up if the mother has had multiple cesarean sections in the past and/or has a placenta previa. If you have had previous cesarean sections and have a placenta previa, talk to your doctor about the risks of placenta accreta.