Yoga -- Try a prenatal yoga routine early in the morning to get your day off to a great start. Yoga helps increase circulation to key muscle groups and will help you control your breathing. This process naturally helps reduce stress and tension and is another great low-impact exercise. Just be sure that the poses you attempt don't upset your already-challenged sense of balance.
Light weight training -- Doing some simple exercises with dumbbells and a light barbell can help strengthen your upper and lower body for better overall fitness. You can build up strength in your upper body with bicep curls and overhead presses and increase strength and improve muscle tone in your lower body with lunges and squats. Just make sure you're not pushing yourself too hard and using light weights with more repetitions to ensure a safe and effective workout.