I taught my baby to say "媽媽"&"爸爸" -- 冇高低音~ coz' my baby will have his own 高低音 whenever he likes la.. no need to teach ..
besides.. "媽媽" & "麻麻" sound sooo alike! if you teach your baby "麻媽".. you won't know if she is calling "媽媽" or "麻麻"~ even i taught my baby "媽媽".... sometimes.. my 99 will say he is calling "麻麻"... while he should be calling "媽媽"....