The garment is intended for a new-born and especially a premature child and surrounds at least the trunk. Its inside is made of material tolerated by the skin and is impermeable to water vapour, at least from the inside outwards. The garment leaves the child's face free and, in those regions where a point on or part of the body remains open, has sealing means to seal the garment against the body. The garment is heat-insulating and intended for use inside and outside the incubator.