The advanced stage of pregnancy can be a truly taxing period for your wife, what with the itchy skin, hemorrhoids, cramps, swelling, discomfort, and fatigue.
Maintaining a healthy posture will help her keep back problems away, while exercising, walking or swimming will make her feel energized. Exercises to strengthen the abdominal muscles and support the back are especially good, though, in accordance with guidelines from the American College of Obstetricians and Gynecologists, she should avoid any exercises done while lying on the back.
What your wife requires most at this point is adequate rest. If she has trouble being comfortable, sleeping on her left, with a pillow under the stomach and between her knees, will help.