Why is the left lateral position preferred for a woman with a cardiac condition in labor?

The left lateral position is preferred for a woman with a cardiac condition in labor primarily to relieve pressure on the heart. In this position, the weight of the uterus is shifted away from the major blood vessels, particularly the inferior vena cava, which can become compressed if the woman is lying flat on her back. This compression can impede venous return to the heart, leading to decreased cardiac output, increased workload on the heart, and potentially worsened cardiac symptoms.

By adopting the left lateral position, the woman can improve venous return and simultaneously enhance uteroplacental perfusion, optimizing blood flow for both the mother and fetus while alleviating strain on the heart. This position can be particularly beneficial in reducing the risk of supine hypotensive syndrome, a condition of low blood pressure that can occur when pregnant women lie flat on their backs.

The remaining options focus on other potential benefits of the left lateral position but do not address the heart's condition as specifically. While decreasing the effect of gravity, improving comfort, and increasing blood circulation also have merit, the primary aim for a woman with a cardiac condition is to mitigate any undue pressure and support optimal heart function during labor.