Which of the following is a risk factor for vitamin K deficiency bleeding in newborns?

Rapid labor is indeed a risk factor for vitamin K deficiency bleeding in newborns. During rapid labor, there may be less time for the baby to receive adequate vitamin K from maternal stores or through the placenta. Vitamin K is essential for the synthesis of clotting factors in the liver, and newborns naturally have low levels of this vitamin at birth due to limited transfer during pregnancy. Rapid labor can exacerbate this situation by reducing the time available for the infant to benefit from any maternal vitamin K status.

In contrast, other options like vitamin K supplementation are a preventive measure against deficiency hemorrhage and would not be considered a risk factor. Assisted delivery may involve the use of instruments, but it does not directly correlate with vitamin K status. High birth weight typically signifies a healthy fetal state and does not specifically increase the risk of vitamin K deficiency bleeding. Thus, rapid labor stands out as an important risk factor in this context.