"Spine development" refers to the growth and strengthening of the bones and muscles in our back, which helps us maintain good posture and perform physical activities. Full definition
Most pediatrician actually are not experts on baby's hip and spine development unless they are also pediatric orthopedic surgeons, which most of them are not. (babywearingschool.com)
The shoulders are rounded (which distinguishes it from the Common Crown Conch) with various degrees of spine development. (AmbergrisCaye.com)
The basics of infant spine development Adult spines are «S» shaped, and feature four slight curves that assist with balance and flexibility. (health-and-parenting.com)