Early Prediction of Placenta Accreta by Ultrasound and Color Doppler

the eligible participants will be searched for signs suggestive of placenta accreta; low implantation of the gestational sac (\<4cm from the external os), presence of placental lakes, Disruption of placental-myometrial interface and trophoblast overlapping a uterine scar by 2 dimensional transvaginal ultrasound and Intraplacental dilated vessels, turbulent blood flows and greatly increased periplacental vascularity by Doppler ultrasound by level II sonographer and co-investigator under his supervision using ultrasound device.