Claire has also been doing it for a few weeks. She absolutely LOVES standing up. She only really does it if she wants me to come and get her, i think. If I put her down in her cot settled, she will just lay down, or sometimes sit up. If I put her down and she is a bit unsettled, she just stands up straight away. It took her about two weeks to learn how to get back down without bumping her head. I dont thnk its really something you can stop her from doing.