What is the correct position for a mother undergoing a fetal nonstress test (NST)?

The appropriate position for a mother undergoing a fetal nonstress test (NST) is semi-Fowler with a pillow under the left hip. This position is beneficial because it helps to optimize uteroplacental blood flow and minimize pressure on the inferior vena cava, which can occur in the supine position. When the mother is positioned semi-Fowler, the slight elevation can aid in comfort and reduce the risk of hypotension due to aortocaval compression from the gravid uterus. Placing a pillow under the left hip enhances this effect, helping to ensure better circulation and fetal heart rate monitoring without compromising the mother's blood flow.

While it is important to avoid positions that may compromise circulation to the fetus or the mother, the other options do not provide the same benefits in terms of minimizing pressure on vascular structures, thus making the semi-Fowler with a pillow under the left hip the most suitable choice for conducting an NST safely and effectively.