So we have a 4tog 120 cm x 150 cm duvet from my older child which he started using at 21 months
My 16month old daughter has never slept through, recently I put her in a fluffy sleep suit, vest and just a blanket. She slept through until 4:45am which is a win as usually she'd be up at 11pm and again at 1/2am. I'll happily take earlier wake ups for the time being than broken sleep and work on the rise time. The thing I think is waking her is her being cold, a blanket just isn't cutting it so wondered when people started using toddler duvets.
She's quite still once she's asleep and checked on usually at 10pm & 2am and we obviously have a monitor (sound only)