Placenta Accreta: Causes, Symptoms Risks &Treatment
Morbidly Adherent Placenta (MAP), as the name suggests, is a placenta that is abnormally attached to the uterus causing complications as it separates, or is attempted to be separated during the delivery. Placenta accreta is one such abnormality of placentation.
What Is a Placenta, and What Is Placenta Accreta?
We all know that after fertilisation, along with the baby, there is another organ known as the placenta that grows in the uterus. Its job is to provide nutrition and oxygen to the growing baby via the umbilical cord. Four days after fertilisation, the zygote attaches to the uterus and starts growing and forming multiple layers. The outer layer is going to form the placenta and the membranes that form the water bag, whereas the inner layer will eventually develop into a foetus.
Placentation begins at the site of attachment of the zygote to the uterus. Normally the placenta invades only the inner layer of the uterus and forms connections with mother’s blood vessels through which nutrients and oxygen will reach the baby (at the same it does not let mother’s blood come in contact with the baby’s).
If, as a result of some abnormality in the uterine wall, the placenta invades deeper into the uterine wall, beyond just the inner layer, it causes placenta accreta. If invasion by the placenta extends into the uterine muscles, this is known as placenta increta. If it penetrates even further, it is known as placenta percreta.
Is It Common?
The incidence of placenta accreta is on a rise in recent times, from 1 in 30,000 pregnancies in the early 1950s, 1 in 4000 in 1970s to 1 in 250- 500 pregnancies in 2000s. Not surprisingly, this increase coincides with the increase in the rate of Caesarean deliveries from 5.5% in the 1970s to 32.8% in 2012. It would not be wrong to say that placenta accreta is an unintended by-product of Caesarean deliveries.
What Are the Causes of Placenta Accreta?
One theory suggests that the damaged innermost layer of the uterine wall promotes placentation at that site and this is what causes placenta accreta. One example is a scar tissue resulting from previous uterine surgical procedures. This explains why a previous uterine surgery, most commonly a C-section, is a major cause of placenta accreta.
Types of Placenta Accreta
Placenta accreta, increta and percreta are the three types of placentation disorders or MAP, all causing similar problems but of varying severity. Placenta accreta is the mildest, and placenta percreta is the most severe as it may involve other organs in the abdomen too.
Common Signs & Symptoms of Placenta Accreta
Placenta accreta symptoms during pregnancy: (What the mother will experience)
1. 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.
2. 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%).
3. 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:
1. 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.
2. 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.
3. 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.
4. Reduced blood pressure and an increase in the pulse rate: This occurs when there is excessive blood loss.
Who Is at Risk of Developing Placenta Accreta
As mentioned above any abnormality or disturbance in the normal structure of the uterine wall predisposes the mother for placenta accreta. Two major risk factors are:
1. A previous Caesarean delivery
2. Placenta praevia or the low lying placenta (placenta covers the cervix, partly or totally).
There is a drastic increase in the incidence of placenta accreta if both these risk factors are present and the risk increases with each subsequent C-section.
The other common risk factors for placenta accreta are:
3. Those who are older than 35 years
4. Those who have been pregnant several times (multiparity)
5. Those who have fibroids under the lining of the uterus (endometrium)
6. Those who have had any surgery on the uterus, including removal of fibroids (myomectomy), dilatation and curettage after an abortion.
7. Those who have disorders of the lining of the uterus, such as Asherman syndrome (scarring of the uterine lining due to an infection or surgery).
Diagnosing Placenta Accreta
Diagnosing during pregnancy:
In at-risk mothers, the healthcare provider will attempt to rule out any abnormality of placentation.
1. Routine ultrasound examination: For the initial diagnosis of placenta accreta, ultrasound done as a routine can accurately diagnose 80% of the times. It is done using a handheld device placed on the abdomen or inside the vagina and is painless.
2. MRI or Colour Doppler: In the remaining 20% cases if ultrasonography is unclear or atypical, for diagnosing placenta accreta, MRI or colour doppler is the investigation of choice.
Diagnosing during delivery:
If placenta accreta was not diagnosed during pregnancy, the diagnosis is clinical and the suspicion is made on the basis of above-mentioned signs. In the case of profuse bleeding, it becomes an emergency with no time for any diagnostic tests. It can only be confirmed in the operation theatre. But when associated with severe placenta previa, the doctor will suspect at the time of a per vaginal examination in the labour room itself even before the delivery of the baby. In this scenario, the doctor may decide to opt for an emergency C-section directly if you haven’t been diagnosed so far with placenta previa.
Treatment for Placenta Accreta
The main aim of placenta accreta treatment is to stop the bleeding, restore the lost blood and save the mother by safely removing the placenta with or without the uterus.
1. Planned Caesarean and Hysterectomy Due to Placenta Accreta: In cases where the diagnosis is made in advance, the medical care provider and the mother should discuss the possible treatment modalities and understand the possible outcomes. Usually, an elective C-section planned around 34 weeks, with hysterectomy (removal of the uterus with the placenta) is the most appropriate choice. This prevents life-threatening complications. But if you have a strong desire to retain fertility, the doctor may attempt conservative uterus saving techniques when the blood loss is minimal. But the outcome is unpredictable and there is no guarantee of a subsequent pregnancy. Most times, it is an on table decision for the doctor and a prior consent for the possible uterus removal will be taken from you for medico-legal purposes.
2. Emergency Laparotomy: If the diagnosis was made after the delivery of the baby, the profuse bleeding and the non-separating placenta call for an emergency laparotomy (a surgery done to open the abdomen and the uterus) with or without hysterectomy.
3. Steroid Injections The Mother: Some doctors may choose to administer a steroid injection to the mother before the planned Caesarean hysterectomy at 34-35 weeks to accelerate the maturation of the baby.
4. Blood transfusions: Massive blood transfusions may be needed to compensate for the blood loss which may be as high as 3-5 litres.
Risks and Complications of Placenta Accreta
The risk to the Mother
1. Life-threatening: Placenta accreta, if not diagnosed and managed in time can be life-threatening. It carries a mortality rate of up to 10%.
2. Loss of fertility: Hysterectomy or removal of the uterus is the treatment of this condition in the majority of the cases. This means that the mother loses all the chances of childbearing in the future.
3. Damage to other organs: There is an increased risk of bladder injury, ureteral injury, pulmonary embolism, need for ventilator use, and an increased risk of ICU admission.
4. Surgery and anaesthesia related risks
The Risk to the Foetus
There is no effect of placenta accreta on the baby. But associated placenta praevia may cause difficulty and delay in the delivery of the baby causing the complications related to delayed labour.
Can Placenta Accreta be Prevented
Primary prevention aims at reducing the risk factors. Plan an early pregnancy (preferably).
A life-threatening complication, placenta accreta can be managed safely with an early diagnosis. Going for routine scans, and being aware of the symptoms can assure timely treatment to mitigate the risks.