Have read your thread with interest, but nothing to add, until now.

Just wondering what made you think that 18.5kg is underweight for a 4 year old? My DS is 106cm (75% percentile) and 17kg (somewhere between 50-75% percentile) and is 4. Just wondering if I have read the growth charts wrong or if you used another method? (I used the growth charts in QLD red book).