Very cute baby.
Picture #1 - I'm really not wild about, but I think that's just my personal preference (as I tend to not really be into selective colouring)
Picture #2 - I find hard to critique because the frame really takes attention away from the picture.
Picture # 3 - Is nice, the image is crisp, though there is a few highlights that appear to be a bit blown out. Those types of things do not normally bother me, but I've had people comment about that on some of my photos. The image could also be more interesting with a shallower depth of field. If you cannot achieve that with your camera, you could always try it post production.
Ok I played with it really quickly to illustrate my point. The edit is not great, but I think it shows how changing the dpeth of field (and the cropping) and reducing a bit of the highlights on the cheek, a bit of visual interest was added:
Picture #4 - Cute profile, but there seems to be something a bit odd with the crop. I think it's because the chin is dissappearing off the picture.. kinda leads the eye out of the picture instead of in. Again a shallower depth of field could add interest to the picture.
I'm not an expert by any means, but I think all in all there is much potential in those pictures and at that age a baby can be hard to photograph.
Oh and another suggestion, keep on shooting, I mean just take as many picture as you can get away with with your shutter speed and memory card, I think with babies it works so much better that way since their facial expressions can change so fast! LOL when I do a photoshoot of my daughter I usually come out with about 200, out of which I'll probably edit and keep 40 - 50 of them.