What is a maternal factor that can contribute to prolonged decelerations?

The supine position of the mother can contribute to prolonged decelerations in fetal heart rate due to the potential for compression of the inferior vena cava. When a pregnant woman lies flat on her back, the weight of the uterus can press against this large vein, which is responsible for returning blood from the lower body to the heart. This compression can reduce blood flow, leading to decreased oxygen delivery to the fetus and resulting in fetal stress, which is reflected as prolonged decelerations in the fetal heart rate.

In contrast, the other options do not typically have the same negative impact. Uterine contractions, for instance, can influence fetal heart rate patterns, but they are not a direct factor like the supine position. A healthy diet and proper hydration are generally associated with positive maternal and fetal outcomes and are unlikely to contribute to complications like prolonged decelerations.