Have you heard of lost wax casting? I think that would be the route to go but you would have to do a positive/negative procedure first with epoxy and RTV: Cast an epoxy positive from your alginate mold, then a RTV negative from this and make the wax positive from the RTV. Then the wax is coated with ceramic slurry, dried, baked in an oven to cure the ceramic and melt out the wax and the final metal casting is made in the resulting ceramic mould. You can get amazing detail but whether it would extend down to baby fingerprint whorls is questionable.
Google 'lost wax casting' and 'investment casting'.