What is the best preventative treatment for supine hypotension in a pregnant patient?

The best preventative treatment for supine hypotension in a pregnant patient is to turn the patient to the left side. This position is effective because it alleviates pressure from the inferior vena cava, which can become compressed when the pregnant uterus rests against it in the supine position. By lying on the left side, blood flow to the heart increases, improving cardiac output and circulation. This is particularly important in the later stages of pregnancy when the uterus is larger and more likely to compress blood vessels when the mother is lying flat on her back.

The other options do not effectively address the issue of supine hypotension. Maintaining a supine position would worsen the problem by increasing pressure on the vena cava. Sitting the patient up straight can be beneficial in some cases but may not provide optimal relief from hypotension as turning to the left side does. Turning to the right side could still allow for some compression of major blood vessels, which does not offer the same relief as lying on the left side. Therefore, turning to the left side is the safest and most effective preventative measure for addressing supine hypotension in pregnant patients.