Slowly lower yourself onto the ball with your partner's help. Sit with knees apart, feet flat on the floor. Rock back and forth or side to side until you find a soothing rhythm. (If you're 5 feet 2 inches to 5 feet 7 inches tall, use a 55 cm ball; if you're 5 feet 7 inches or taller, opt for a 65 cm.)
What it does: Opens the pelvis, helping the baby descend through the birth canal.