A major means of mobility in infancy, consisting of forward motion with weight supported by the infant's hands (or forearms) and knees.

Crawling is the primary form of mobility achieved by infants before they learn to walk. Babies have a primitive crawling reflex at birth, which is instinctively activated when they are placed on their abdomens. Their legs flex, and they move forward, raising their heads to free them for motion. However, this reflex disappears during the early weeks of life, and true crawling is not learned until the second six months, normally around the same time that an infant is able to sit up alone for extended periods of time. The learning process, which occurs gradually, is usually completed by the age of nine to ten months.

Even before they can crawl, infants find other methods of moving about. For most babies, creeping—wriggling or slithering forward...