I've just come back from the GPs with DD2. Ostensibly, I went to talk to her about DD2's reflux. Actually, I went to get her to measure DD2's head and examine her fontanelles and tell me if her brain growth was normal. She's 25th centile for head circ and 91st for weight so quite out of proportion and of course DD1 has a brain overgrowth condition, so although an undergrowth condition wouldn't be related - you can't help wondering...
Actually, I've been more than wondering. I've been obsessing about it and waking up at night and catching myself staring at her teensy little head and working myself up to the point where I feel physically sick with fear for her.
Of course the GP looked her over and said she was perfectly fine, please go away. 
I was just wondering if this worrying was normal - because it's turned out that pretty much every other piece of loony behaviour of mine has turned out to be a perfectly normal part of the whole SN rollercoaster.