The "newborn scrunch"—where a baby pulls their knees to their chest and curls their arms in—is a completely natural behavior known as "physiological flexion." For nine months, the baby was tightly tucked into the fetal position in the womb, and their muscles and joints have "memory" of this compact space. In the first few weeks after birth, their muscle tone is still dominated by these flexor muscles, making them look like they are constantly trying to curl back into a ball. Additionally, the scrunch is often a response to sensory overstimulation or a way to find comfort in a world that suddenly feels too big and open. It can also be a physical reaction to gas or digestive discomfort, as pulling their legs up helps them put pressure on their abdomen to relieve bubbles. In 2026, pediatricians emphasize that this "scrunchy" phase is a sign of healthy neurological development. As their core strength increases and they spend more time in "tummy time," they gradually "unfurl," but that initial compact posture remains one of the most endearing and recognizable traits of the "fourth trimester" of human development.