Placenta previa

Definition:

A condition that may occur during pregnancy when the placenta implants in the lower part of the uterus and obstructs 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, or abnormal formation of the placenta. The incidence of placenta previa is approximately 1 out of 200 births. The incidence increases with each pregnancy, and it is estimated that the incidence in women who have had 6 or more previous deliveries may be as high as one in 20 births. The incidence is doubled in multiple pregnancy (such as twins and triplets). Risk factors include multiparity (previous deliveries), multiple pregnancy, and a previous C-section if the scar is low and close to the vaginal cervix region.