In the womb and for a period of time following birth, a baby's spine is shaped like the letter C. This curve is termed a primary curve, which is Kyphotic. During the time the baby is learning to lift his head and eventually walk, muscles develop. As muscular strength and ability is gained, the baby's activity will shift body weight to the spine. Gradually secondary curves develop in the cervical and lumbar regions; Lordotic curves. These curves will continue to develop until growing stops.
Spinal curves are either kyphotic or lordotic. In a normal spine there are four types of spinal curvatures important to balance, flexibility, and stress absorption and distribution: