What incidence level increases the risk of shoulder dystocia in a multiparous patient during the second stage of labor?

The risk of shoulder dystocia in a multiparous patient during the second stage of labor increases when two hours or more have elapsed without an epidural due to the possibility of prolonged labor. Without the analgesic benefits of an epidural, there may be less optimal uterine contractions and maternal positioning, contributing to inadequate fetal descent and rotation. This impaired descent can significantly increase the likelihood of shoulder dystocia, which occurs when the baby's shoulder becomes lodged against the mother's pelvic bone during delivery.

In contrast, prolonged labor with the use of an epidural is typically associated with more effective pain management and potentially fewer complications from maternal fatigue. Thus, while extended durations of labor without effective analgesia can raise the risk of delivery complications, the presence of an epidural can mitigate these risks through better control of pain and enhancement of labor progression.