Your placenta is essential for the survival of your baby. It’s a specialist organ that develops in the uterus only during pregnancy.
It’s the only organ of the body which grows within another organ.
It’s also the only organ the body will attempt to dispose of once its job of supplying nutrients to your baby is complete.
For more placenta facts read What Is A Placenta? 13 Amazing Placenta Facts.
When does the placenta develop?
The placenta begins to grow very early on, around week 4, and will be fully formed by the time you’re 12 Weeks Pregnant. Around this time the placenta will take over from the yolk sac and corpus luteum and take on the job of nourishing your baby.
This helps to stabilize your pregnancy hormones and improves those pesky early Pregnancy Symptoms.
From this point onward, everything your baby needs to survive and thrive will pass through the placenta.
The placenta attaches to the uterine wall and, over the next 28 weeks, will grow and mature alongside your baby.
By the end of your third trimester the placenta will weigh around 1.5 pounds (o.7 kgs).
What is placenta accreta?
Although rare, there is a possible pregnancy complication known as placenta accreta.
Placenta accreta occurs when the placenta attaches too deeply into the uterine wall.
Ordinarily, the placenta detaches from the wall of the uterus after the baby is born.
In cases of placenta accreta, the placenta is not able to detach in the same way. It might only partially detach from the wall of the uterus, and might require surgical removal.
Placenta accreta makes delivery of the placenta very difficult at the time of birth and increases the risk of serious complications, including severe bleeding.
Related reading: Placenta Accreta | Symptoms & Risk Factors
Placenta accreta spectrum
Placenta accreta spectrum is an umbrella term used for a number of similar placental abnormalities, which we will discuss below.
The differences between the three conditions relates to the depth to which the placenta has grown within the uterus.
Placenta accreta occurs when the placenta grows too deeply into the uterine wall.
Placenta increta occurs when the placenta grows too deeply into the uterine muscle.
Placenta percreta occurs when the placenta grows through the uterine muscle and invades other nearby organs, such as the bladder.
Placenta percreta is the most serious of the placenta accreta spectrum conditions.
Medical professionals often use the term placenta accreta when referring to any of the 3 variations.
What causes placenta accreta?
No one knows exactly what causes placenta accreta spectrum, but the most common explanation is thought to be a pre-existing defect in the lining of the wall of the uterus.
This then leads to abnormal ‘anchoring’ of the placenta.
These abnormalities can result from scarring caused by previous uterine surgery or a previous cesarean section.
Pregnant women who have Placenta Previa, where the placenta partially or fully covers the cervix are also at higher risk of placenta accreta.
How common is placenta accreta?
Placenta accreta is rare but is thought to occur in around 1 in 7,000 births.
Rates are on the increase, however, due to a rise in clinical risk factors, most notably the global increase in rates of cesarean section.
According to the American Pregnancy Association, placenta accreta accounts for around 80% of all placenta accreta cases, with 15% experiencing placenta increta and only 5% experiencing placenta percreta.
How is placenta accreta diagnosed?
Sometimes placenta accreta is not discovered until the time of birth; most women, however, will be diagnosed antenatally.
Placenta accreta might be suspected during your routine ultrasound. If so, you will be referred for a magnetic resonance imaging (MRI) scan to help with the diagnosis.
Antenatal diagnosis of placenta accreta is preferable so that careful antenatal and birth planning can take place.
Placenta accreta makes for a more complicated delivery. Depending on your individual circumstances, vaginal birth might not be recommended, due to the risk of heavy bleeding at the time of birth.
You might require a c-section, or your baby might need to be born prematurely.
Babies born earlier than their due date are more likely to need to spend time in a neonatal intensive care unit (NICU), where they will be given some extra care for breathing support or for other complications associated with premature birth.
Women with known risk factors for placenta accreta should be referred to a fetal medicine specialist as early as possible.
Placenta accreta ultrasound
If you have been diagnosed with placenta accreta, ultrasound investigation is important. Your doctor or care provider will arrange for you to have additional ultrasound scans to access the extent of the developing placenta accreta.
Signs of accreta can be present as early as the first trimester but are more commonly found in the second and Third Trimester.
Placenta accreta can also present itself even in the absence of ultrasound findings; therefore, it’s important to understand who might be at risk for placenta accreta.
Those with risk factors for placenta accreta should be referred early on for ultrasound investigation.
Risk factors for placenta accreta
There are several risk factors for placenta accreta. The condition can also occur in women without any risk factors, although this is rare.
Risk factors include:
- Previous cesarean section. The incidence of placenta accreta increases with each prior cesarean delivery
- Previous fibroid removal or other uterine surgery. This causes scarring on the wall of the uterus
- Placenta previa. This occurs when the placenta attaches low in the uterus, partially or fully covering the cervix. Placenta accreta is present in 5-10% of cases of placenta previa
- Advanced maternal age. Women over 35 years old are most at risk
- Fertility treatment, including in vitro fertilization (IVF)
- Multiparity. This when women have had more than one pregnancy (greater than 20 weeks gestation)
- Asherman Syndrome. This rare condition causes scar tissue in the uterine wall and cervix.
For more about who is at risk of placenta accreta read Placenta Accreta – Symptoms And Risk Factors.
Placenta previa
Placenta previa is another placental location abnormality; the term literally means that the placenta is ‘presenting first’. In other words, in cases of placenta previa, the placenta attaches in the lower part of the uterine wall and lies close to the cervix, or covers it.
As the placenta develops, it will grow between the cervix and the baby. This increases the risk of vaginal bleeding and, if the placenta covers or partially covers the cervix, rules out the option of delivering vaginally.
If you have a Low Lying Placenta, meaning it’s close to the cervix but not covering it, the chances for vaginal delivery are much improved.
Placenta previa is a significant risk factor for placenta accreta. Placenta accreta spectrum occurs in 3% of women diagnosed with placenta previa with no prior cesarean section.
This risk increases to 3%, 11%, 40%, 61%, and 67% for the first, second, third, fourth, fifth, or more cesarean deliveries, respectively.
Placenta accreta symptoms
Women with placenta accreta are at risk of severe vaginal bleeding, particularly at the time of birth.
However, the problem is that some pregnant women with placenta accreta will have no symptoms or vaginal bleeding at all.
As we know, placenta previa often develops with accreta, and women with placenta previa often present with vaginal blood loss in the third trimester.
Occasionally, in cases of placenta percreta, the placenta can grow through the uterus and attach to organs such as the bladder. If this is the case, a woman might present with pelvic pain or blood in the urine.
If you experience any Vaginal Bleeding or pain after your first trimester, you should contact your care provider straight away for advice.
Why is placenta accreta a concern?
Women diagnosed with any of the placenta accreta spectrum conditions will be classed as having a high risk pregnancy.
Women with placenta accreta are at risk of severe bleeding, often requiring blood transfusion and uterine surgery to correct it.
If you’ve been diagnosed with placenta accreta, you’ll most likely be referred to a maternal fetal medicine specialist for further treatment and management of the condition.
In cases where accreta has been diagnosed antenatally, you will be advised to give birth in a high level hospital setting – a facility capable of dealing with complex obstetric complications, with access to multi-disciplinary staff (critical care nurses, doctors, haematologists, and neonatologists) and access to a blood bank.
Is placenta accreta life threatening?
Those with placenta accreta are at risk of maternal morbidity and even maternal death because of severe and sometimes life threatening blood loss.
Sometimes placenta accreta is only diagnosed at the time of birth, potentially requiring immediate emergency care, access to an obstetric theatre and neonatal unit, and blood transfusion services.
In severe cases, or in settings where heavy vaginal bleeding cannot be managed appropriately, placenta accreta can be life threatening.
Major obstetric hemorrhage that cannot be controlled effectively can lead to serious complications in the mother, including death.
Complications include:
- Dangerously low blood pressure
- Loss of consciousness
- Lack of oxygen to vital organs
- Problems with blood clotting
- Multiple organ damage, including kidney failure, lung failure, and damage to other major organs.
Additional risks to the mother
Unfortunately, severe bleeding and other associated risks of hemorrhage aren’t the only risks of placenta accreta for the mother.
Although blood loss is major risk of placenta accreta, there are other additional risks:
Surgical birth
A vaginal birth might not always be possible. If accreta is diagnosed in the pregnancy, your care provider might recommend a scheduled delivery.
A c-section birth could be advised, to minimise the chances of an emergency occurring at the time of birth. That way birth can take place in a controlled environment where there is access to all necessary medical interventions, if required.
Surgical intervention
Women who give birth vaginally are likely to require surgery to remove the placenta and control the bleeding.
In some cases, if surgical removal of the placenta is likely to cause life threatening blood loss, a hysterectomy might be the safest option.
What are the risks of placenta accreta for the baby?
Placenta accreta won’t directly affect the developing fetus. However, women with placenta accreta are at increased risk of Preterm Birth, either as a result of heavy bleeding in pregnancy, or a scheduled c-section birth around 35-37 weeks.
If there is heavy bleeding during the pregnancy, which causes the mother to become unwell, this could also cause problems for the baby. It might potentially involve an even earlier birth than planned.
Related reading: Premature Babies – What To Expect Week By Week.
Placenta accreta treatment
Unfortunately, there is nothing that can be done to prevent placenta accreta from occurring, and nothing that can be done to treat it during the pregnancy once it has been diagnosed.
The placental location and the extent to which it has embedded in the uterus will not change throughout the pregnancy.
Therefore, all that can be done antenatally is to plan for the most appropriate method of birth to minimize complications for both mother and baby.
Severe cases of placenta accreta are treated with surgery. Your care provider will performed a c-section birth to deliver your baby. After your baby is born the surgeons will then attempt to surgically remove your placenta as safely as possible, with minimal damage to the uterus.
If it’s believed that the surgical removal of the placenta could be complicated, or that part of it might not be able to be removed without causing substantial bleeding, the safest option might be to perform a hysterectomy.
Removing the uterus with the placenta still attached inside reduces the chances of excessive bleeding.
However, this also removes any chance of becoming pregnant again in the future.
Another more controversial option for treatment is to leave the placenta attached inside the uterus after the birth of the baby. Medications are given to contract the uterus, prevent infection and control the bleeding. The placenta is then reabsorbed by the body; this method is said to be successful in 80% of cases.
Does placenta accreta affect future pregnancies?
If you have a diagnosis of placenta accreta, and wish to have more children in the future, it’s important to discuss this thoroughly with your care provider.
If you’ve had a previous pregnancy complicated by placenta accreta spectrum, the chances of it occurring again are quite high.
Women with a history of placenta accreta are at increased risk of the following in a subsequent pregnancy:
- Repeat placenta accreta spectrum (including placenta increta, and percreta)
- Postpartum hemorrhage (PPH)
- Placenta previa
- Surgical intervention
- Preterm birth
- Damage to the uterus and other pelvic organs
- Hysterectomy
- Maternal death.
In severe cases of placenta accreta, the uterus might need to be removed in order to deliver your baby (and placenta) in the safest possible way. In these rare occurrences, sadly, it will not be possible to get pregnant again in the future.
A cesarean hysterectomy will only be performed as the last possible resort, to preserve the life of mum and baby, if bleeding cannot be controlled, or if agreed ahead of time.
Antenatal diagnosis of placenta accreta is essential. An important part of care planning is to have discussions with many different specialists; planning should also involve counseling.
If you’re unsure about your options, speak to your care provider early. This will give you the best chance of having the birth that’s right for you.
