Which variation of umbilical cord insertion is least associated with increased fetal mortality and morbidity?

The least association with increased fetal mortality and morbidity is found with marginal (Battledore) insertion of the umbilical cord. In this type of insertion, the umbilical cord attaches to the edge of the placenta rather than the central portion. While it may present some risks, such as potential issues with the placenta's ability to function, studies have shown that marginal insertion typically does not lead to as high a risk of complications as other variations.

Central insertion of the cord is usually seen as the norm and is associated with a lower risk profile; however, it does not highlight variations that can contribute to specific complications. Velamentous insertion, where the fetal vessels separate from the cord before reaching the placenta, is associated with higher risks including vessel rupture and fetal hemorrhage, which are significant concerns during labor and delivery. Complete insertion is a term that is less commonly used in clinical contexts and can suggest a few different potentials for abnormality, but does not provide a specific context for risk evaluation.

Overall, marginal insertion has been recognized in many studies as having a more favorable outcome in comparison to those configurations that involve more significant detachment or potential injury to fetal vessels. Thus, marginal (Battledore) insertion is associated with a better fetal prognosis