Is the baby blanket for your baby? If so, great.
If not...think about this: will the mother of the baby be willing to handwash the blanket? Is the cotton yarn washable? The cotton yarns, expensive or cheap, that I have seen are not washable.
I knit a beautiful Aran baby blanket (using cotton) for my daughter's new son...and she has 'babied' the baby blanket...and it is still beautiful 3 years later. But she gave me her solemn promise: if I knit her a cotton baby blanket...she would handwash and lay flat to dry.
She has seen what becomes of cotton anything when it is washed and dried and washed and dried...such as my Sugar and Cream dishcloths.
They fade, warp, shrink and distort! Generally atrocious looking a few months later.