Localization of the embryo in the lower part of the gestational sac at 6-7 weeks' gestation is associated with placenta previa

Objective: To evaluate whether placenta previa is associated with ultrasonographic findings during the first trimester. Methods: A case-control study with 1:5 (34 and 170 cases with placenta previa and normal placenta) matched pairs was conducted to compare ultrasonographic findings, including the position of the gestational sac (GS), that of the embryo in the GS, and placental cord insertion from 5-11 weeks of gestation. Results: Embryos located in the lower part of the GS at 6-7 weeks of gestation were observed in 83.3 and 17.1% of the cases and the controls, respectively. Placental cord insertion in the lower third of the uterus at 9-11 weeks of gestation was observed in 38.3 and 6.7% of the cases and the controls, respectively. Conclusion: Low embryo localization and low placental cord insertion during the first trimester was associated with placenta previa.