The largest percentage of children not seen within the age range was at 3.5 years, where half of children had their contact before the lower age threshold.
Cafodd pob plentyn 3.0 o gysylltiadau gan ymwelwyr iechyd ar gyfartaledd, y nifer isaf a gofnodwyd, gan barhau â'r duedd ar i lawr ers i'r data gael eu casglu gyntaf.