Aim: To study the relation of umbilical cord insertion (CI) site in early gestation and placental development from the chorion villosum. Methods: We ultrasonically measured the distance between the internal cervical Os and the CI site (CID), the distance between the internal cervical Os and lower placenta edge (PLD), and placental thickness at early (10-12 weeks) and mid-gestation (18-20 weeks). Results: CID in early gestation (CID-Early) correlated with CID in mid-gestation (r 2 s0.171;

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... . CID-Early correlated with PLD in mid-gestation (r 2 s0.093; P-0.01). Thickness of chorion villosum or placenta in early gestation did not correlate with that at mid-gestation. Increasing thickness of placenta was significantly higher in long CID-Early (G20 mm) cases than short cases (-20 mm) (P-0.05). Conclusions: The process of placental development and the placental location are affected by CI location at early gestation, and suggests that this process might be affected by poor blood supply from the low uterine segment when CI site is close to the internal cervical Os.