Northern Ireland's women were beaten 2-0 by group leaders Iceland in their latest European Championship qualifier in Reykjavik on Saturday night.
The home team dominated throughout and had gone close on a number of occasions before Holmfridur Magnusdottir put them ahead on 37 minutes.
Fanndis Fridriksdottir added the second goal on 53 minutes.
Alfie Wylie's side remain fourth in the group on 11 points ahead of Wednesday's game with Belgium at Windsor Park.
Iceland move to 22 points in Group C - a point ahead of Norway who defeated Belgium 3-2 on Saturday.
The Belgians are on 17 points - six ahead of the Irish - heading into Wednesday's concluding qualifiers.
Bulgaria are bottom of the group having lost all their nine games.