You could do this:
Code:
Sub resizeMerge()
Dim lRow As Long
Dim lCount As Long
Dim lLastRow As Long
lRow = 1
' change to your last row
lLastRow = 25
Do While lRow <= lLastRow
With Cells(lRow, "A")
If .MergeCells Then
lCount = .MergeArea.Cells.Count
.UnMerge
If lCount > 2 Then .Resize(lCount - 1).Merge
End If
End With
lRow = lRow + lCount
Loop
End Sub