What's the point of weighing young kids?

I've been pondering the value of weighing young kids (babies and toddlers) for a while now and the issue was raised again in the Age this week (I couldn't find the link but oddly the enough they ran a similar article in January) which argued for school children to be routinely weighed.  It seems there may be some justification for this age gruop in terms of getting better data Australia wide, and potentially for older kids where you really want to address obesity issues but I'm not convinced of the value at the individual level for really young kids and especially for babies.  This is the cohort that is currently routinely weighed and the data used to plot them on a percentile chart.  However, babies come in all shapes and sizes and there is not much that parents can do about it.

My thoughts were initially provoked by a routine check at the maternal and child health nurse which found that our 8 month old had dropped from the 75th percentile in weight to the 25th.  This worried the nurse which ultimately worried me.  It took me a long time to work through the fact that he had been sick and vomiting for a couple of weeks but ultimately that he is happy and progressing well in all other ways.

This made me wonder what value the weighing process had added?  It made me worry and it triggered a discussion about how he was doing fine.  But if he hadn't been doing fine (i.e. if he'd been lethargic or unresponsive or inactive) wouldn't that have been the discussion anyway regardless of his weight?  If you've got a seriously underweight baby, wouldn't you have noticed that too?

The other thing that made me think it was pointless was that the nurse had basically no advice on what to do in response - i.e. how to bulk up a baby - or whether this is a possible thing to do.  She suggested giving him custard and maybe more meat but it turns out he isn't keen on either of these things.  So even if weighing babies identifies a 'problem' there is nothing that can really be done for it.

While I know that it is unlikely that maternal child health nurses will stop weighing little kids at their regular checks, I think it is important that we parents don't buy into it too much.  Some babies and toddlers will be in the lower percentiles and some will be in the higher percentiles and that's ok.  If you're doing all the regular things (breastfeeding or bottle feeding, starting your baby on mashy solids) and your baby is doing all the regular things (being responsive and active and happy at least some of the time), then there is really nothing to worry about...although we all undoubtedly find things to worry about regardless.