This is one of those knits that I wish my baby would never grow out of. I just might have to rewrite the pattern again in an even bigger size, so he has a vest to wear next fall too! The pattern is from thrifty knitter, the cobblestone inspired "manly vest." It is written in a small 0-3 month size, so I added more stitches in an attempt to make it bigger. It perfectly fits my 15+ pound 4 month old son right now.
One of the best parts of the vest are the buttons - which are on one of the shoulders and all the way down that same side. So it is really easy to get on and off a squirmy baby. I also just really love the simplicity of it - it's a knit that requires minimal finishing (you only have to sew together the non-buttoned shoulder), and that is the kind of knitting that I prefer since I really hate seaming together knitted pieces.
For knitters who want to know how I made this bigger, here are the details: I used Jo Sharp Silkroad Aran Tweed and size 6 needles. I cast on 90 stitches and used a wrong-side row of S1 K4 P37 K7 P37 K4. I did buttonholes every 12th row (rows 7, 19, 31, 43, 55) and knit a total of 57 rows before dividing for armholes. I had 9 stitches on either side of the bound off neck rather than 8. That's all there is to it!