Placentas with velamentous cord insertion have a lower vessel density. As the growth of the fetus is dependent on the organization, mass, and nutrient-transfer capacity of the placenta, fetal development is hence hindered in velamentous cord insertion. This can lead to fetal malformations and low birth weight. The umbilical vessels may also be longer compared to normal, particularly when the site of velamentous cord insertion is in the lower uterine section as the extension of the uterine isthmus as pregnancy advances causes vessel elongation. This results in increased vascular resistance, which impedes nutrient transfer to the fetus.
