An inflatable airbag assembly (100, 300, 400, 500, 600a, 600b) comprising: a housing to be mounted to a seatback of a seat of a vehicle; a first inflator; and an inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) to receive inflation gas from the inflator, and to deploy from a packaged state within the housing to a deployed state extending forward from a side of the seatback, whereby the inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) in the deployed state is to be positioned laterally adjacent to a vehicle seating position, the inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) comprising: a first chamber (120, 320, 420, 520, 620a, 620b) to be inflated by the inflation gas to a first pressure and to be positioned to receive a torso of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, and a second chamber (130, 330, 430, 530, 630a, 630b) to be inflated by the inflation gas to a second pressure greater than the first pressure and to be positioned to receive one or more of a shoulder and a pelvis of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, wherein the first chamber is formed from the inboard and outboard panels, wherein the second chamber (130, 330, 430, 530, 630a, 630b) is disposed within and occupies a portion of the first chamber (120, 320, 420, 520, 620a, 620b), wherein the first chamber is formed from an inboard and an outboard panel (122, 124), characterized in that the inboard and outboard panels (122, 124) are formed of a single unitary fabric panel, the single unitary fabric panel folded along a fold line and coupled along an upper distal coupling, a lower distal coupling, and a rear distal coupling, wherein the upper distal coupling, the lower distal coupling and the rear distal coupling are formed of a continuous seam, and wherein the second chamber couples to the first chamber along the upper lower and rear distal couplings. a housing to be mounted to a seatback of a seat of a vehicle; a first inflator; and an inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) to receive inflation gas from the inflator, and to deploy from a packaged state within the housing to a deployed state extending forward from a side of the seatback, whereby the inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) in the deployed state is to be positioned laterally adjacent to a vehicle seating position, the inflatable airbag cushion (110, 310, 410, 510, 610a, 610b) comprising: a first chamber (120, 320, 420, 520, 620a, 620b) to be inflated by the inflation gas to a first pressure and to be positioned to receive a torso of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, and a second chamber (130, 330, 430, 530, 630a, 630b) to be inflated by the inflation gas to a second pressure greater than the first pressure and to be positioned to receive one or more of a shoulder and a pelvis of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, wherein the first chamber is formed from the inboard and outboard panels, wherein the second chamber (130, 330, 430, 530, 630a, 630b) is disposed within and occupies a portion of the first chamber (120, 320, 420, 520, 620a, 620b), wherein the first chamber is formed from an inboard and an outboard panel (122, 124), characterized in that the inboard and outboard panels (122, 124) are formed of a single unitary fabric panel, the single unitary fabric panel folded along a fold line and coupled along an upper distal coupling, a lower distal coupling, and a rear distal coupling, wherein the upper distal coupling, the lower distal coupling and the rear distal coupling are formed of a continuous seam, and a first chamber (120, 320, 420, 520, 620a, 620b) to be inflated by the inflation gas to a first pressure and to be positioned to receive a torso of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, and a second chamber (130, 330, 430, 530, 630a, 630b) to be inflated by the inflation gas to a second pressure greater than the first pressure and to be positioned to receive one or more of a shoulder and a pelvis of an occupant moving in a direction transverse to a longitudinal axis of the vehicle, wherein the first chamber is formed from the inboard and outboard panels, wherein the second chamber (130, 330, 430, 530, 630a, 630b) is disposed within and occupies a portion of the first chamber (120, 320, 420, 520, 620a, 620b), wherein the first chamber is formed from an inboard and an outboard panel (122, 124), characterized in that the inboard and outboard panels (122, 124) are formed of a single unitary fabric panel, the single unitary fabric panel folded along a fold line and coupled along an upper distal coupling, a lower distal coupling, and a rear distal coupling, wherein the upper distal coupling, the lower distal coupling and the rear distal coupling are formed of a continuous seam, and wherein the second chamber couples to the first chamber along the upper lower and rear distal couplings.