a married womans husband was . is regarded to be the father of her child even if that was / is not the case
sometimes when a child was chirstened the vicar / curate etc. would put a note in the margin of the reputed fathers name if it was known, i have seen a bp. entry for a child where the mother is Elizabeth and the vicar / curate says she say the fatehr is her husband but he cannot be as he has been away serving (or at Sea) for a year!
(or words to that effect)