One factor known to increase the risk of cot death is an overheated baby. Babies lose excess heat from their heads and whilst it is a good idea to cover baby’s head outside if it is cold or windy, once in the house, the baby’s hat should be removed. The baby’s hat should also be removed when you enter an area that is warm, such as on a bus or going into a shop, even if it means waking baby1.
There are some babies that need to wear a hat indoors. These are babies that were born prematurely, of low birth weight or have difficulty maintaining their temperature. Once these babies are of a certain healthier weight or are able to maintain their body temperature, the hat should be removed indoors2.
1FSID and DoH (2007) Reduce the Risk of Cot Death. DH Publications, London
2 Fraser DM, Cooper MA, eds (2003) Myles' Textbook for Midwives 14th ed. Churchill Livingstone, Edinburgh.