Forest had arrived at the DW on top of the Championship with 10 points from a possible 12 but they were second best for the first half, when all the goals were scored.
Referee Craig Pawson awarded them a free-kick on the edge of the area after Leon Barnett fouled Henri Lansbury.
And Reid stepped up to curl a beauty past Carson, in off the near post.
Wigan were level six minutes later through Maloney's penalty, after Marc-Antoine Fortune was brought down by Jack Hobbs.
And they scored what proved to be the winner in the 35th minute when Fortune's shot was tipped on to the bar, allowing Gomez to tap home.
Forest nearly conceded a third in added time when James McCarthy broke down the left, but his ball across was behind substitute James McClean and the chance had gone.