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Placenta previa

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Definition:

Placenta previa is a condition that may occur during pregnancy when the placenta implants in the lower part of the uterus and is close to or covering the cervical opening to the vagina (birth canal).

Causes, incidence, and risk factors:

Possible causes of placenta previa include a scarred endometrium (lining of the uterus), a large placenta, an abnormal uterus, or abnormal formation of the placenta. The incidence of placenta previa is approximately 1 out of 500 births.

The incidence increases with each pregnancy, and it is estimated that 1 in 20 women who have had 6 or more previous deliveries are at risk. The rate of placenta previa is doubled in multiple pregnancy (carrying more than one baby).

Risk factors include multiparity (previous deliveries), multiple pregnancy, previous myomectomy (removal of uterine fibroids through an incision in the uterus), and a previous C-section (if the scar is low and close to the vaginal cervix region).

• Review Date: 8/19/2005
• Reviewed By: Sharon Roseanne Thompson, M.D., M.P.H., Clinical Fellow, Department of Obstetrics & Gynecology, Brigham and Women's Hospital, Boston, MA. Review provided by VeriMed Healthcare Network.

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