Lie on your back with knees bent in a tabletop position and your baby propped against your thighs. Squeeze the ball between your knees, placing one hand behind your head and one hand on your baby to steady him.
Inhale, then exhale as you draw your abs in and lift your head and shoulders off the floor, looking at your baby. Hold for 10 seconds, working up to 15. Lower your head and repeat.