It's a discontinued yarn, but it's listed as 270 yds to 4 oz., or 247 meters to 113 g. The recommended gauge was 5 sts = 1" on US size 7/4.5mm needles, and it was 100% wool. As for substitutes, Paton's Classic Wool would be perfect, the exact same gauge recommendation, so the fabric would come out with the same drape.
But because it's for a baby, you might want to make it out of acrylic or bamboo, because some infants react to wool. As long as the gauge is supposed to be 5 sts to 1", you're okay. I know your pattern says 5.5 sts = 1", but that's okay-- you're just trying to match the thickness of the yarn, so if the yarn to yarn recommended gauge matches up, you're good.