Abstract: The enveloping rigid shell (A), made in one piece, comprises a hood (2) protecting the head of the child, a bottom (1) forming a back or cradle, a seat (3), a gutter (4) for the legs, a movable foot rest in the gutter. To be appropriate for use as a baby carrier, straps for the horizontal transport are provided and for use as a push chair these straps allow in cooperation with a groove (37) the attachment onto a foldable carriage, with three attachment means onto the frame (B): two buckles (15) with ratchet mechanism of a same type of security belt on either side of the shell, a notch (20) into which a small tongue (33) from the base of the frame penetrates. The frame (B) of which the periphery is complementary to that of the shell (A) comprises anchoring means (34,36) onto a back of the seat of the vehicle and fixing means (18,33) for the rapid unhooking from the shell (A). It further comprises a protecting shield of flexible material arranged so as to receive the child in case of a shock.