Which umbilical cord variation is least likely to be associated with increased fetal mortality and morbidity?

The marginal or battledore insertion of the umbilical cord refers to the cord attaching to the edge of the placenta rather than the center. While it can sometimes be associated with certain complications, it is generally considered to have a lower connection to increased fetal mortality and morbidity compared to the other variations.

In contrast, velamentous cord insertion, where the cord inserts into the membranes rather than directly into the placenta, poses a higher risk of complications due to the vessels being more exposed, which can lead to vessel rupture and compromised blood flow to the fetus. A single umbilical artery indicates that one of the two expected arteries is absent, which is associated with various congenital anomalies and increased risk of morbidity. A short umbilical cord can limit fetal movement and may lead to complications such as cord accidents or placental detachment.

Marginal insertion is important to monitor, but it is recognized for having less severe implications than the other variations, which is why it is considered the least likely to be associated with increased fetal mortality and morbidity.