I have not seen baby leg warmers. I would just measure baby's legs circumference and length. decide how long you want them/ with or without a turnover. If you want them to go over tights or leggings/ loose or snug then do a swatch in the design and yarn you like to figure out how many stitches you need. then go from there. I love the idea of legwarmers for baby's, my two year old is always kicking off her blanket in the pushchair so you always worry if they are warm enough in the winter. Good luck.