Why do strangers think it's OK to criticise your child's progress?

Remember the last time someone approached your teenage child and expressed concern over their developmental progress?

“14?! And you're still out and about with your mum?!” “15 and you're still only 5'3”. Is your mummy not feeding you at all?”

Yeah, me neither.

So, why do veritable strangers deem it appropriate to pass comment on the progress of your younger children?

Thankfully, I'm past the stage where randomers will remark on my children's developmental milestones, but a close of friend of mind has yet to make it through to the other side.

The mum of a beautiful 16-month-old toddler, Alison is also sporting a generous bump as she awaits the arrival of her second child,.

During a time when she should be basking in the glow of family life, instead she spends most of her days fending off comments about both her pregnancy and her daughter.

“Has she got her five words yet?”

“She's not making friends on her own? Oooh, I'd keep an eye on that.”

“Shouldn't she be a little taller by now? I'm sure my Katy had a good inch or two on your little one at her age.”

Time must have dulled my memory because while I know I dealt with similar, the fury I felt on my friend's behalf during a recent day out was almost palpable.

“Only six months? You must be expecting a horse!”

“Were you as big with the little'un as you are now?”

“At your size it must be hard to give the little one enough attention. I hope Mummy isn't neglecting you.”

What is it about this particular stage in a parent's life when they and their children are considered fair game in society's eyes?

No topic is off-bounds; no subject matter too sensitive to broach with a stranger at a busstop.

Some people suggest it's simply a lack of manners while others put forward the theory that, for a small minority, becoming a parent renders them an expert in the field.

I couldn't care less what the reason is for these people's lack of compassion, but nothing justifies the disregard they show for fellow mothers and their offspring.

Tutting over a rash on a child's cheek - as one stranger did to my friend's daughter last Saturday- is no different to me approaching that person's teenage son and rolling my eyes at the smattering of pimples decorating his forehead.

But I wouldn't because it's just not what you do.