The changes are being made after a thorough examination of the evidence from Public Health Wales and bring Wales into line with changes made elsewhere in the UK.
Gwneir y newidiadau hyn ar ôl archwiliad trylwyr o’r dystiolaeth gan Iechyd Cyhoeddus Cymru, a bydd Cymru’n ymuno â gwledydd eraill y Deyrnas Unedig sydd eisoes wedi rhoi’r newid hwn ar waith.