What is the primary risk associated with a breech presentation?

The primary risk associated with a breech presentation is umbilical cord prolapse. In a breech presentation, the fetal buttocks or feet are positioned to come out first instead of the head. This position can lead to the umbilical cord being compressed during delivery, as the presenting part is not well positioned to protect the cord. If the cord slips down ahead of the presenting part, it can become trapped between the baby's body and the birth canal, resulting in cord prolapse. This situation can cause a decrease in oxygen supply to the fetus, leading to potential complications such as fetal distress.

Other risks such as placental abruption, preterm labor, and increased delivery time are relevant in obstetric situations, but they are not the direct or most critical concern that specifically arises with breech presentations. Thus, focusing on umbilical cord prolapse as the primary risk highlights the unique anatomical and delivery considerations that arise when a fetus is in a breech presentation.