I've had three babies in the NICU, I don't care for them so I wouldn't make them too heavy. Babies at home are not incased in darkness to sleep and a NICU is a stepping stone to getting a baby home. They treat them like birds, put a blanket on them and its time to sleep. That's just my parental point of view...I had a set of preemie twins and a single in the unit. Cotton would be my suggestion and hopefully the babies are looking at the designs and not the dark side. Jmho