A cocoon sleeping bag is a swaddle sleeping bag for the little ones. In the first 3 months, babies like to be wrapped nice and tightly to feel that secure feeling of mom's belly. Your newborn also has a startle reflex, which means it can easily wake itself up with its arms. All this makes swaddling a perfect solution in the first months. With closed armholes, baby is really swaddled and cannot wake himself up with his arms.