Matilda goes through a behavioural "challange" for around 2 weeks before each developmental change. So at 9 months she started having great tantrums and at 9 1/2 months she started walking, at 11 months she picked up the tantrums again and at 12 months she started putting 2 words together etc etc etc... it got to one point where I was wondering what was going to happen next because of her behaviour.

Oh! Yeah as well she stopped sleeping during the night, she would be awake for 2 hours in the middle of the night. Almost every major developmental milestone was pre-empted by no sleep.