Placenta accreta often causes no signs or symptoms during pregnancy — although vaginal bleeding during the third trimester might occur.

Occasionally, placenta accreta is detected during a routine ultrasound

Placenta accreta is thought to be related to abnormalities in the lining of the uterus, typically due to scarring after a C-section or other uterine surgery. Sometimes, however, placenta accreta occurs without a history of uterine surgery.

Many factors can increase the risk of placenta accreta, including:

• Previous uterine surgery. The risk of placenta accreta increases with the number of C-sections or other uterine surgeries you've had.
• Placenta position. If the placenta partially or totally covers your cervix (placenta previa) or sits in the lower portion of your uterus, you're at increased risk of placenta accreta.
• Maternal age. Placenta accreta is more common in women older than 35.

Previous childbirth. The risk of placenta accreta increases as your number of pregnancies increases.

Placenta accreta can cause:

• Heavy vaginal bleeding. Placenta accreta poses a major risk of severe vaginal bleeding (hemorrhage) after delivery. The bleeding can cause a life-threatening condition that prevents your blood from clotting normally (disseminated intravascular coagulopathy), as well as lung failure (adult respiratory distress syndrome) and kidney failure. A blood transfusion will likely be necessary.
• Premature birth. Placenta accreta might cause labor to begin early. If placenta accreta causes bleeding during your pregnancy, you might need to deliver your baby early.