Abstract: A vented baby bottle assembly and a baby feeding system having a plurality of vented baby bottle assemblies is provided. The baby bottle assembly includes a bottle with at least one venting notch in the mouth of the bottle, and an artificial feeding nipple fastened thereto. When the feeding nipple is fastened to the mouth of the bottle, a sealing region on the feeding nipple forms one or more, one-way, negative-pressure, relief valves at the location of the venting notch(es) for allowing air to enter the bottle when suction is applied to the nipple-tip by a child. The feeding system includes a plurality of stages with a separate bottle assembly corresponding to each successive stage. At each successive stage, the volume of the bottle in the assembly is equal to or greater than the bottle from the assembly in the preceding stage.