When a baby is born in a hospital they are usually wrapped in a blanket or hospital swaddle to promote safe sleep in the child. Swaddling involves wrapping the baby completely with its arms at its side (or up if they prefer). It helps calm the baby and allows it to sleep more easily.
The original blanket or swaddle that was used for newborn babes in the US was invented by the Illinois-based Kuddle-Up healthcare supply company that was founded by A. L. Mills in 1920. He gave the blankets their distinctive blue and pink striped design and they are still in use today.
There are also more modern alternatives called wearable blankets that are easier for parents to use. They support natural arm and hand movements made by the baby and some come with sleeves that have foldover mitten cuffs that can be closed when the baby is asleep.