A swaddling blanket and sleepsack are similar in terms of comforting baby and helping her sleep, but are used at different stages in baby’s development, never at the same time. In short, a swaddle is a large, thin blanket that wraps baby up like a burrito, limits mobility and is commonly used during the first three months of life. A sleepsack is made of thicker material, often used around or after three months of age, allows more mobility but still helps baby feel contained. A sleep sack is a wearable blanket that is a safer alternative for babies who are still at risk for SIDS (under one years old).
Both a swaddle and sleepsack keep baby warm and snug, as if they were in the womb; and if you read the baby books, that’s exactly where your newborn longs to be.