We do not recommend using the Snugglebundl overnight. We have spoken to the Lullaby Trust for advice on this issue. They inform us that the main reason for not advising absorbable fabrics in a cot is due to bacteria build up if they are left in soil for long periods of time. We can only advise not to use the Snugglebundl overnight. Just in case, we have made sure it is tested for breathability and safety.