Abstract: A seat assembly comprises a booster seat with a lower support surface and an upper seating surface. A back support extends upwardly at the rear of the upper seating surface and side supports extend from the back support around the lateral edges of the seating surface to merge with the upper seating surface. A supplementary base has a peripheral edge to engage the periphery of the lower surface to provide increased lift. The base has an aperture dimensioned to receive the back support and side supports so that the base may be inverted and nested on the upper seating surface.

Abstract: A seat structure for a baby or young infant that can facilitate an anterior pelvic tilt and hip abduction, while supporting the infant in an upright position. The infant seat structure described herein comprises a seat that is forward tilted. A pommel is provided at a forward edge of the seat that is wide enough to splay the infant's legs, provides support for the infant, and maintains their position in the seat structure. The infant seat structure also includes a back support and side supports to support the infant's/baby's upright position. The side supports do not extend substantially forward past the infant's hip joints, and therefore allow for substantial splaying of their legs. A infant's legs are able to project outwardly from the seat structure on either side of the pommel, through the two spaces that are each situated between the pommel and side supports.