Worried about my baby's position...?

When I went in for my 20 week checkup/ultrasound the lady noted that the baby was breech and her legs were not tucked in front of her; She was in a kneeling position. Can the baby move head-down? When? I'm scared she is going to stay "upright" throughout my whole pregnancy - which will probably lead to a c-section. (21 weeks pregnant today).