Daisy hasn't done this yet but i know it is coming.... My other daughter (13) used to do this and it frightened the life out of anyone who saw it. She would get so upset with herself during a tantrum that she would stop breathing, it was awful and could last up to 40 seconds. We sometimes had to tip her up and pat her back quite hard to get her to take a breath...... She did grow out of it, but all this came flooding back to me last night when Daisy was crying, it all sounded exactly the same, she only held her breath for a few seconds but that's how it started with Gemma. Does anyone elses LO's do this? I did mention it to my HV at the time and she said it was quite normal, frightening but normal.