I don't think it's something they can consciously control, they need the hormone that reduces urine production while they sleep. I believe a drug can be prescribed if necessary to assist with this - but I don't think usually it's considered a problem till a child is past 7 or 8 If a child sleeps deeply, or bed wetting runs in the family, that's also a factor Lifting a child when you go to bed yourself, and holding them over the toilet (they don't wake!) is moderately effective but doesn't actually help them with learning to wake at night themselves Anyway, good luck Potty by the bed (be prepared for it to get kicked over though!) Double layer of sheets on the bed as suggested, good mattress cover, spare duvet, some thick towels to throw down of necessary