"I do not make sandwiches for my husband."
Translation:Nie robię kanapek dla mojego męża.
I guess it depends on what you call 'irregular'. A lot of words that have 'ą' in a closed syllable (like mąż), have 'ę' in an open syllable (like mę-ża).
This is due to a historical loss of yers (very short vowels). This same process was also the reason for kościół (ko-ściół) and kościoła (ko-ścio-ła)