Baby due in March. We have gone for a moses basket for the first 6 months and got some cellular blankets and sleeping bags for when baby is a bit bigger. Practised today tucking the blankets in under the mattress in the moses basket to make it a tight and safe sleeping space but the blankets are so big that to have them in one layer means tucking absolutely loads of the blanket under the mattress. This has meant that the mattress no longer looks flat at that end as there's so much blanket under the mattress. I know the mattress should be flat. The blankets are standard Mothercare cellular blankets so not sure what I'm doing wrong. Can anyone advise?