Note as there are few (less than 100) mothers aged under 16 and 45 or over, there may be large year-to-year changes due to natural volatility.
Sylwer: gan nad oes llawer o famau dan 16 oed a thros 45 oed i’w cael, efallai y ceir newidiadau mawr o flwyddyn i flwyddyn oherwydd anwadalrwydd naturiol.