When a child always lies on his left side to sleep, can it make his rib development assymetric?

Possibly: This is potentially more likely in an infant that cannot roll over at all. In older children sleeping on one side should not make ribs develop asymmetrically as the child is up and moving all day. We are all asymmetric ...I have had success with chiropractic adjustments, massage, and craniosacral therapy resolving such asymmetry as these release fascia and muscles that can misalign the bones.

Wouldn't worry: The 9-12 hours a day your kid sleeps is never going to be only in one position, they all shift and roll. They also spend the balance of the day alert in many positions. Rib symmetry is dictated by genetic and growth factors and can become worrisome during the rapid growth of the teen years. Regular monitoring (checkups) helps identify changes early.