Placenta previa mouth is associated with all of the following except:
Placenta previa is implantation of the placenta partially or completely over the lower uterine segment. Damage to the endometrium or myometrium due to previous surgery or infection can predispose to low implantation and placenta previa.
Risk factors for placenta previa:

Prior surgery (cesarean section / Myomectomy Hysterotomy)
Previous uterine curettage
Endometritis
Increasing maternal age (>35 years)
Increasing parity
Placental size –increased (as in multiple pregnancy)
Placental abnormality –Succenturiate lobe
Smoking (due to defective decidual vascularisation)
Elevated prenatal maternal serum alpha fetoprotein levels (unexplained)
Large placenta
Previous C. S. scar
Primigravida
Previous placenta previa