DD (almost 16m) has started leaking through her nappy at night quite regularly. I'm not sure how to stop this. She's in a toddler size nappy that is meant to go up to 15kg and she's only 11.5kgs. If I put her in a bigger nappy it's too loose and she leaks anyway. I don't really want to wake her up and change her nappy during the night. She has a bottle before bed but apart from that, not excessive amounts of water in the late afternoon/evening. Any ideas?