The maternity nurse understands that vascular volume increases 40% to 45% during pregnancy to:

Choice A reason: This is incorrect because venipuncture for blood work should be avoided on the affected arm. The mastectomy may have involved the removal of lymph nodes, which can impair the lymphatic drainage and increase the risk of lymphedema (swelling) in the arm. Venipuncture can cause further damage or infection to the arm.

Choice B reason: This is correct because the BP cuff should not be applied to the affected arm. The BP cuff can exert pressure on the arm and interfere with the blood and lymph flow. This can also increase the risk of lymphedema or pain in the arm.

Choice C reason: This is incorrect because the affected arm should not be held down close to the woman's side. The woman should be encouraged to elevate the arm above the level of the heart and perform gentle exercises to promote circulation and prevent stiffness. The arm should not be immobilized or restricted.

Choice D reason: This is incorrect because the affected arm should not be used for IV therapy. IV therapy can introduce fluids or medications into the arm that can affect the blood and lymph flow. It can also cause irritation or infection to the arm.

Choice A reason: Vascular volume increases during pregnancy to meet the increased oxygen and nutrient demands of the fetus, not to compensate for decreased renal plasma flow. In fact, renal plasma flow increases by 50% to 80% during pregnancy to facilitate the excretion of metabolic wastes.

Choice B reason: Vascular volume increases during pregnancy to ensure adequate blood supply to the uterus and other organs, not to prevent maternal and fetal dehydration. Dehydration can occur due to vomiting, diarrhea, or inadequate fluid intake, and it can be prevented by drinking enough fluids and replacing electrolytes.

Choice C reason: Vascular volume increases during pregnancy to provide adequate perfusion of the placenta, which is the main organ of gas exchange and nutrient delivery for the fetus. The placenta receives about 10% of the maternal cardiac output at term.

Choice D reason: Vascular volume increases during pregnancy to support the growth and development of the fetus and the maternal tissues, not to eliminate metabolic wastes of the mother. Metabolic wastes are eliminated by the kidneys, lungs, skin, and gastrointestinal tract.