A baby sleep sack is a wearable blanket designed to keep infants warm and safe during sleep by eliminating the need for loose bedding in the crib. Often referred to as a “baby sleeping bag,” it features a fitted neck and armholes to prevent the fabric from sliding over the baby’s face, significantly reducing the risk of suffocation or SIDS. These sacks typically zip or snap shut, providing a cozy, cocoon-like environment that allows for healthy hip movement while preventing the baby from kicking off their covers and getting cold during the night.