From the comments:

kit_the_brave: Aw, he looks so happy! As he should be. Why did she put the baby on the ground instead of handing her to him? Or, you know, just walking off with her again?

Anonymous: I think it was a Roman custom to give the father the choice to pick up the baby or not. If he picked it up they kept it. If he didn’t the child was exposed. It was a ritual.

pikku_gen: I think it was a pretty gruesome thing, but then again… it was a men’s world. Also if a man had any doubt whether the child was his, he might not have picked it up. That might not have meant the child was to be exposed, but neither would it have been raised as a legal child.

klio: Indeed. There might have been multiple factors contributing to origins of the action: connecting the newborn with the generative power of the earth, the chthonic spirits, the ancestors; allowing an unobstructed view for the midwife to assess the infant’s body and movements; and, most infamously, allowing the presumed father the choice to accept the child or leave it where it lay. A ritual that might not even have been performed in some households, but which would be an important rite under some circumstances.

Born with ritual, lifted from the ground with ritual, announced to the community with ritual, after a certain number of days named with a ritual… each step of the way not just a celebration, but a public affirmation of the child’s place and legitimacy in the tribe/community/religion, and a sigh of relief that the infant had survived one more milestone and could now be considered really here, and not just quickly passing through. Oh, and then you could go fill out some bureaucratic birth-registry paperwork in the city of Rome, if you were so inclined. I say, never forget the paperwork. You might want to run for emperor some day.