There was no one way of recording the death of a stillborn child in Italy. Most times you will see only a death record created (and not a birth record) and it will note that the child was born "senza vita" or "without life."
Occasionally, stillborn births will be recorded separately, often amongst the death records of town residents who died elsewhere. Below is a death record created for a stillborn birth whose form was pre-printed for this purpose. I have not come across pre-printed stillborn birth/death records very often. The title reads "Atti di Morti Nati" or "Act of Dead Birth".
Death Record for Stillborn Female Child of Nicolo di Sergio and Rosa Latuno
What I find fascinating is the fact that normal procedure was to present a child at the civil record's office to have it's birth recorded. When someone died the civil record's official often came to the person's home to visually verify that the person was dead. One has to wonder whether they carried the body of their baby to the town hall or if the civil official came to their home as would have been done for any other death.