A mattress system (1) is disclosed comprising a mattress (2) with an upper face (3) and a lower face (4), said upper face comprising a cavity (5), which is enclosed by a side face, placed adjacent one end (6A) of the mattress and shaped to accommodate at least the head (7) of a child (35), where the mattress system further comprises a first mattress segment (9), which is arranged so that it can be placed in and fill out the cavity of the mattress, such that the upper face of the mattress appears intact and coherent, and where the mattress system also comprises additional mattress segments (10), which, with an upper face thereof, are arranged to abut parts of the lower face of the mattress.
