Objective: To describe the relationship between the degree of placental histologic villous mineralization (VM) and stillbirth in aneuploid and euploid fetuses.Methods: The extent of VM for aneuploid and gestational age-matched euploid placentas was graded semiquantitatively on a 0 to 3 scale based on the number of terminal or stem villi containing mineralizations in forty x10 fields of view. The extent of VM was analyzed in relation to fetal status at delivery (liveborn or stillborn) for both aneuploid and euploid fetuses. Results: For 14 available aneuploid placentas, grade 0 or 1 VM was recorded for seven aneuploid specimens, of which two were stillborn. Grade 2 or 3 VM was recorded for seven aneuploid specimens, of which six were stillborn. Fourteen gestational age-matched euploid placentas served as controls. Grade 0 or 1 VM was observed in nine euploid specimens, of which four were stillborn. Grade 2 or 3 VM was observed in five euploid specimens, of which four were stillborn. For aneuploid fetuses, stillbirth was significantly more frequent with grade 2 or 3 VM compared with grade 0 or 1 VM (chi(2) = 4.667, P .05).Conclusion: Histologic VM is not a universal finding in, or exclusive to, stillbirths. Aneuploid but not euploid stillbirths show increased histologic VM compared with livebirths. This may implicate impaired placental or circulatory function as a mechanism for death in aneuploid fetuses.