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).
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