The diagnosis of time of death is often complex and it is even more difficult in the case of a fetus dead in-utero affected by macerative post-mortal phenomena. The criteria currently available in scientific literature can turn to be inappropriate or useless in clinical practice, where the medical examiner often experience a complete mismatch between morphological and clinical data. The present work arises from the necessity to update these thanatological criteria. After a review of the literature so far, the actual validity of thanatological criteria has been assessed through a retrospective stury of a selected population. Thereafter it has been developed an experimental prospective phase with an experimental macerative protocol, in order to identify possible stages of cell degeneration positively correlated to the time of death: interesting data emerged from the electron-microscopy analysis as a progressive vacuolization of cell structures within 24-hours after death. This workshould be especially useful to medical examiners, forensic pathologists and gynecologists who want to better understand fetal death for forensic or clinical purposes.