Placenta Accreta – When The Adherence Of The Placenta Is Disturbed

In the placenta accreta, the placenta (placenta) grows into the muscles of the uterus. As a result of impaired placental adhesion, parts of the placenta may remain in the uterus at birth. In this case, the expulsion of the placenta may be delayed and infections and heavy bleeding may occur. Here you can learn how placenta accreta develops and how it is treated.

What Is Placenta Accreta?

Placenta accreta is a disorder of placental adhesion in which the tissue of the placenta (placenta) grows into the muscles of the uterus. Normally, the placenta detaches from the uterine wall after birth. In the placenta accreta, the placenta remains partially or even completely attached to the uterine wall.

Placenta accreta is a serious pregnancy complication because it usually leads to heavy bleeding at birth because the placenta cannot detach on its own.

What Is The Importance Of The Placenta In Caring For The Baby?

The placenta consists of tissue from the mother and the baby and is already formed in the first weeks of pregnancy. With the chorionic villi, the placenta adheres to the uterine wall.

The placenta has the following functions:

  • Supply of the baby until birth and removal of its metabolic products. During this process, embryonic tissue grows into the endometrium.
  • Production of hormones that are important for maintaining the pregnancy.
  • Influence on the maternal immune system: rejection reactions towards the baby are eliminated. The placental barrier protects the baby from many harmful substances and pathogens.

The effectiveness of the placental barrier depends on the size and properties of the molecules that wish to pass through the barrier. Many toxins are retained by the placental barrier. However, alcohol, nicotine, and various drugs can pass unimpeded from the mother’s bloodstream to the baby’s bloodstream. Pathogens can also be passed on to the child. Developmental disorders or miscarriages can be the result.

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As pregnancy progresses, not only the child grows, but also the placenta. Around the time of birth, the placenta weighs about 500 grams, measures about 20 centimeters in diameter, and has a thickness of two to five centimeters.

From the very beginning, the placenta has to control its own growth and adapt its functionality to the needs of the baby. It thus assumes a special function compared to other organs. After birth, the placenta usually detaches from the uterine wall and is expelled by the afterbirth (afterbirth).

During the healing and regression phase after the afterbirth is expelled, the blood vessels that connect the mother’s body to the placenta close.

How Does A Placenta Accreta Form?

In placenta accreta, the solution disorder of the placenta develops at the very beginning of pregnancy. The placenta does not just grow into the uterine mucosa – as would be normal – but connects with the uterine muscles.

Like all hollow organs, the uterus consists of three layers of tissue:

  • Outer layer (perimetrium or serosa): a smooth, shiny coating.
  • Middle layer (myometrium): smooth musculature.
  • Inner layer (endometrium): uterine lining.

During pregnancy, the endometrium is also called the decidua or the decidua. In the presence of a placenta accreta, this means in medical language that the tissue of the placenta has penetrated the decidua.

  • In three-quarters of cases, the classic form of placenta accreta is present. In this case, the placenta has penetrated completely or only partially through the decidua (endometrium) to the uterine musculature (myometrium). However, the ingrowth of the musculature is relatively weak.
  • In about 20% of cases, a placenta increta is formed. In this case, the placental tissue grows intensively into the uterine musculature.
  • In about 5% of women, a placenta percreta develops. In this case, the placental tissue breaks through the outer layer of the uterus and forms growths in other organs, especially in the bladder.

In the case of placenta accreta, the placenta cannot detach on its own after birth. Thus, the maternal blood vessels cannot close. Instead, placenta accreta results in an open wound after birth, which can lead to high blood loss.

During each of the prenatal checkups, the doctor checks the position of the placenta and assesses whether there could be complications during delivery. Learn more about the last prenatal checkups during your pregnancy here.

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What Are The Causes Of Placenta Accreta?

Doctors suspect a connection between the increasing frequency of cesarean births and the increasing frequency of placenta accreta. According to this study, a cesarean section increases the likelihood of placenta accreta in a subsequent pregnancy. The more cesarean sections performed, the higher the risk of placenta accreta. In the 1950s, placenta accreta occurred in only 1 in 30,000 pregnancies; in the 2000s, it affected 3 in 1000 pregnancies. During this period, the number of cesarean sections performed also increased sharply.

The development of placenta accreta is also favored by other surgical procedures and by uterine anomalies. However, placenta accreta can also develop without the above conditions.

Placenta accreta often occurs with placenta praevia (placenta previa), which is understood to be a deep attachment of the placenta.

How Common Is Placenta Accreta?

Placenta accreta is very rare. According to U.S. data, it occurs in 1 in 500 to 1 in 2,500 births. As the number of cesarean sections increases, so do the cases.

What Is Placenta Praevia?

A placenta praevia, or anterior placenta, is a positional abnormality of the placenta in which it pushes in front of and partially or completely covers the internal cervix.

The malposition of the placenta can be pronounced in different ways:

  • Deep-seated placenta: The placenta does not touch the cervix, but it sits unusually close to the cervix.
  • The placenta touches the cervix but does not cover it (placenta praevia marginalis).
  • The placenta partially covers the cervix (placenta praevia partialis).
  • The placenta completely covers the cervix (placenta praevia totalis).

Placenta praevia always indicates a high-risk pregnancy. The malposition of the placenta can be life-threatening for mother and child. The main danger is the occurrence of heavy bleeding. During the mild contractions that occur in the last weeks of pregnancy, the lower uterine segment, in particular, is stretched. If individual placental villi then detach in placenta praevia, vaginal bleeding may occur. These are painless and typical of placenta praevia. Towards the end of pregnancy, however, premature placental abruption may occur, accompanied by severe pain and bleeding. However, premature placental abruption is very rare in placenta praevia.

In the case of placenta praevia, the course of pregnancy should be closely monitored. Patients are often prescribed strict bed rest and should avoid physical stress.

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Vaginal delivery is not possible if the placenta completely covers the cervix. In this case, delivery is always by cesarean section. This should be done before the onset of labor to reduce the risk of bleeding. Even if there are no symptoms, a cesarean section is usually planned for as early as the 36th or 37th week of pregnancy.Here you can find out more about the special features of placenta praevia.

What Are The Risk Factors For Placenta Accreta?

Pregnant women are more likely to develop placenta accreta in the following cases:

  • Scarring in the uterus as a result of a previous cesarean section.
  • Covering of the cervix by the placenta (placenta praevia).
  • Deep-seated placenta: higher risk because the mucosa at the bottom of the uterus is slightly thinner than in the middle of the uterus.
  • Age over 35 years.
  • Pregnant women who have been pregnant several times before.
  • Fibroids located under the lining of the uterus (endometrium).
  • Previous surgeries of the uterus in which fibroids were removed.
  • Disease of the endometrium: For example, in Asherman’s syndrome the endometrium scars as a result of infection or surgery. When the placenta grows, there may be a disorder of placental adhesion.
  • Smoking.

Symptoms And Medical Examinations

Often, placenta accreta is not associated with any discomfort or symptoms during pregnancy. Thus, the expectant mother usually does not feel anything. In the last trimester of pregnancy, vaginal bleeding may occur, which must be checked by a doctor immediately. Your gynecologist will always consider placenta accreta and/or placenta praevia as the cause of these symptoms and examine you accordingly.

Placenta accreta is usually detected during one of the routine ultrasound examinations. If placenta accreta is suspected during a routine ultrasound examination, a vaginal ultrasound examination can provide more detailed information. Early diagnosis is often difficult. A definite diagnosis by ultrasound is not possible in every case. Ultrasound can often only determine the position of the placenta.

Initially, there is no danger for the baby or a deficiency in supply. However, if you experience heavy bleeding before the expected delivery date, it may be necessary to terminate the pregnancy prematurely. Bleeding usually only occurs at a time when the child is safely viable

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What Are The Treatment Options?

If placenta accreta is detected before birth, doctors almost always advise a cesarean section to minimize the risks from heavy bleeding and delayed delivery. If placenta praevia is present at the same time, this additionally argues for a cesarean section. In these cases, a cesarean section is a least risky solution.

In natural birth, the placenta is detached manually. This often requires curettage (scraping). In principle, natural birth is possible with a placenta accreta if no placenta praevia is blocking the birth canal.

A placenta increta or percreta, on the other hand, always requires a cesarean section. If placenta accreta is discovered before birth, the baby is first delivered by cesarean section and then the placenta or – in severe cases – the entire uterus including the placenta is removed. If the placenta cannot be detached from the uterine wall, removal of the uterus (hysterectomy) is inevitable.

Learn more about which placenta positions require a cesarean section. Read our article on the position of the placenta at 30 weeks of pregnancy to learn more.

Planning An Earlier Delivery

Pregnant women with placenta accreta should plan for earlier delivery date. If a cesarean section is under discussion, it is usually performed between 34 and 36 weeks of pregnancy.

Due to heavy bleeding, affected women sometimes require a blood transfusion to compensate for blood loss. Expert treatment is therefore required. Not every woman is affected by heavy bleeding. Placenta accreta can occur in a variety of forms.

What Are The Consequences For Later Births?

Women who have already had placenta accreta are often recommended a cesarean section for subsequent pregnancies, although the problem does not necessarily recur in the next pregnancy. Your doctor will pay special attention to placental abnormalities (placenta accreta or placenta praevia) during ultrasound examinations. If there is no abnormality, a cesarean section is not necessary.


Placenta accreta is an abnormal attachment of the chorionic villi to the uterine wall, in which the placental tissue grows into the uterine muscles. During childbirth, undetected placenta accreta can be dangerous because the placenta cannot detach on its own, delaying the birth process and causing heavy bleeding. Doctors usually recommend a cesarean section. In subsequent pregnancies, this placental anomaly does not necessarily have to recur, although the risk is increased.

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