While I know they technically received baths while we were still in the hospital, I tend to consider a baby's real first bath when it is done at home.
I think that we may have waited a day or possibly two before giving the girls their first bath, I mean really how dirty can they possibly get while sleeping? Both of my other children had a birth weight of over 8 lbs, so that is the last memory in terms of size that I can recall. Alice and Grace both came home under 6 lbs and while that may not sound like that much difference, in percentage numbers, it is 25% smaller!
At first they were pretty ticked off that they were undressed and being held like a watermelon. Since the cord was still attached, we opted for the sponge bath, this was not comforting for either of them to say the least, but we pushed through it and they both survived.
One nice side effect of having a bath and washed hair is you get to see the hair in a really fuzzy state. Makala's hair was pretty long at birth (1-3) inches and when it was washed she appeared to have just had her finger removed from the electrical outlet. Not so much with Alice and Grace, though Alice does have more and longer hair than Grace.