Pregnant trauma patients should be placed on the left side to:

Placing pregnant trauma patients on the left side is crucial for preventing compression of the vena cava, which can occur when the patient lies supine (on their back). The inferior vena cava (IVC) is a major blood vessel that returns deoxygenated blood from the lower body back to the heart. In the later stages of pregnancy, especially during the third trimester, the enlarged uterus can exert pressure on the IVC when the mother is lying flat. This can lead to reduced venous return to the heart, decreased cardiac output, and potentially result in maternal hypotension.

By positioning the patient on her left side, this compression is alleviated, promoting better blood flow back to the heart and improving overall circulation. This position enhances maternal perfusion and subsequently benefits fetal circulation as well. Adequate perfusion is vital for maintaining oxygen and nutrient delivery to the fetus, making this positioning critical in trauma scenarios.

The other choices, while they touch upon important considerations for pregnant patients in trauma, do not explain the primary reason for side-lying positioning as effectively as the prevention of vena cava compression does.