Although spinal curvature (or curvature of spine) can refer to the normal concave and convex curvature of the spine, in clinical contexts, the phrase usually refers to deviations from the expected curvature, even when that difference is a reduction in curvature. Types include kyphosis, lordosis, and scoliosis. The thoracic and sacral (pelvic) curves develop in the fetus. Around 6 months after birth the cervical curve appears which helps hold the head up. Around one year of age the lumbar curve develops which helps with balance and walking. The cervical and lumbar curves are considered secondary curves whereas the thoracic and sacral curves are primary.