The placenta is an organ that develops in the uterus during pregnancy. Its purpose is to nourish the baby. Oxygen and nutrients pass through the placenta to the baby. Waste products pass back out to the mother’s blood stream.

Placenta previa occurs when the placenta becomes implanted near or over the cervix. The cervix is the lower part of the uterus that opens into the vagina. With this condition, the placenta may cover part or all of the cervix. This condition is only diagnosed after 20 weeks of gestation.

Placenta Previa
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Possible causes of placenta previa include:

  • A scarred endometrium—the lining of the uterus
  • A large placenta
  • An abnormal uterus
  • Abnormal formation of the placenta

Placenta previa can cause problems in pregnancy and birth. These include:

  • Abnormal bleeding, sometimes heavy
  • Premature separation of the placenta from the uterus
  • Premature birth
  • Emergency cesarean (c-section) delivery
  • Problems with penetration of the placenta into the uterine muscle or through the entire uterine wall