Background: Implantation is the communication method between the embryo and the endometrium that allows the fetus receives nourishment and oxygen from the mother. We aimed to determine the relationship between the gestational sac implantation site and future placental site in women with or without a cesarean section (CS) scar, and whether this scar could affect the future placental location. Methods: This prospective cohort study included 192 pregnant women with a singleton pregnancy (97 women with a CS scar and 95 without). Transvaginal ultrasound was done before ten weeks of gestation to assess the implantation site, distance from the lower edge of the gestational sac to the internal os, the relation of the gestational sac midpoint to the uterine midpoint, and retro-chorionic Doppler. At 34 weeks, the placental site was assessed using transabdominal ultrasound. Comparative analysis was performed between the two groups. Results: There were no significant differences in the implantation site, the relationship of the gestational sac to the uterine midpoint, and the placental location between the two groups (P= 0.596, 0.692, and 0.536, respectively), with a high prevalence of posterior implantation, gestational sac above the uterine midpoint and posterior placentation. Correlation analysis showed a highly significant dependence between the placental site and implantation site (r=0.950, P<0.001). Conclusions: The previous mode of delivery does not affect the gestational sac implantation site and future placental site. However, sonographic assessment of the gestational sac implantation site could be useful in predicting the placental location.