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.
Y ganran fwyaf o blant na chafodd eu gweld o fewn yr ystod oedran yw 3.5 mlwydd oed, lle cafodd 56% eu cyswllt cyn y trothwy oedran isaf.