Ok my kid is 3 and very small. Between the 2nd and 9th percentile. She's always been very small... born overdue so 'big' ... Just below the 25th percentile (!!), settled down by 2 months between the 2nd and the 9th. The average height for a woman in my family (both sides) is 5 foot to 5"3, slim/sturdy. I was on heparin when pregnant, the known side effect it small but otherwise healthy children.
She has mild constipation and has seen a paediatrician over it. They looked at her red book and said there were no growth concerns although she was "petite". It was caused by withholding rather than digestive ills and is managed with stool softener and a once a day poo routine: paediatrician says it's a simple case, and she now poos well.
Every so often someone says something intimating I've overlooked something and my child 'should' be taller (usually allergies, illnesses or what I feed her or some internet thing like that survey of how tall you'd be if you lived in the developing world). I get myself really worried.
When 2 short people DTD they make a short kid Yeah? 
She's developmentally average/bright-ish, very very active, rarely sick, eats normal amounts for her age and not really fussy about food.
Who else out there has a small but healthy kid? I'm getting myself all paranoid and guilt ridden when she's seen a Dr and is following her line height/weight wise.
I had PNA focused on her health and I think this might be the dregs of that.