All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
It is permissible for a man, whether a father or else, to change the nappy of a female infant whom one does not usually desire for sexual intercourse as the term 'Awrah (parts of the body that should be covered in Islam) does not apply to her at her age. It is for this reason that the scholars are of the view that it is permissible for men wash the body of a dead a suckling girl or girls around this age. However, if it is possible for her mother or sister to bath her, then that is more appropriate.
Allaah Knows best.