The volume of the chorion villosum is associated with the location of the umbilical cord in the first trimester

Aims: To clarify whether villous placental volumes in cases with low cord insertion (CI) are smaller than those with normal cord insertion. Methods: A prospective cohort study was conducted to evaluate the association between location of umbilical CI and placental volume at 11 to 13weeks' gestation. An ultrasound examination was performed to measure the crown-rump length, the distance between the histological internal cervical os and the CI site, the placental volume, and the uterine arterial blood flow. To standardize the distribution of the ultrasonographic measurements, we transformed data by crown-rump length-weighted linear regression. Results: Six hundred fifty-nine subjects were analyzed. Scatter plots showed a slightly positive correlation between the z-scores of the distance from the CI site to the internal cervical os and villous placental volume (r=0.102, p=0.009) and a negative correlation between the z-scores of the villous placental volume and the uterine arterial pulsatility index (r=-0.165, p<0.001) as well as the uterine arterial resistance index (r=-0.187, p<0.001). Conclusion: The placental volume was likely to be smaller in cases with CI located in the lower uterine segment.