What are the most common placental problems?

During pregnancy, possible placental problems include placental abruption, placenta previa and placenta accreta. These conditions can cause potentially heavy vaginal bleeding. After delivery, retained placenta is sometimes a concern. Here's what you need to know about these conditions:

• Placental abruption. If the placenta peels away from the inner wall of the uterus before delivery — either partially or completely — a condition known as placental abruption develops. This can deprive the baby of oxygen and nutrients and cause you to bleed heavily. Placenta abruption could result in an emergency situation requiring early delivery.

• Placenta previa. This condition occurs when the placenta partially or totally covers the cervix — the outlet for the uterus. Placenta previa is more common early in pregnancy and might resolve as the uterus grows.

  Placenta previa can cause severe vaginal bleeding during pregnancy or delivery. The management of this condition depends on the amount of bleeding, whether the bleeding stops, how far along your pregnancy is, the position of the placenta, and your and your baby's health. If placenta previa persists late in the third trimester, your health care provider will recommend a C-section.

• Placenta accreta. Typically, the placenta detaches from the uterine wall after childbirth. With placenta accreta, part or all of the placenta remains firmly attached to the uterus. This condition occurs when the blood vessels and other parts of the placenta grow too deeply into the uterine wall. This can cause severe blood loss during delivery.

  In aggressive cases, the placenta invades the muscles of the uterus or grows through the uterine wall. Your health care provider will likely recommend a C-section followed by removal of your uterus.

• Retained placenta. If the placenta isn't delivered within 30 minutes after childbirth, it's known as a retained placenta. A retained placenta might occur because the placenta becomes trapped behind a partially closed cervix or because the placenta is still attached to the uterine wall. Left untreated, a retained placenta can cause severe infection or life-threatening blood loss.