Objective: Stillbirth is a devastating obstetric outcome. Although several diagnostic work-up including autopsy, karyotyping is recommended, placenta pathology is the most commonly performed without revulsion by patients. We aimed to investigate the cause of stillbirth by gestational age (GA) group and identify the differences of placental pathological findings among the groups. Methods: We performed a retrospective analysis of placenta pathologic findings of stillbirth including referred cases in our institution from July 2012 to December 2018. We excluded cases therapeutic terminations due to maternal condition. We divided the study population according to the GA at delivery as follows; Group 1, 16+0 to 23+6weeks; Group 2, 24+0 to 27+6weeks; Group 3, 28+0 to 31+6weeks; Group 4, 32+0 to 36+6weeks; Group 5, ≥37+0weeks). Placental pathology was assessed by a single pathologist according to Redline’s criteria, which specifies maternal and fetal inflammatory response, maternal under-perfusion, fetal vascular thrombo-occlusive disease, and chronic inflammatory lesion as recommended by the Society for Pediatric Pathology in the Unites States. Results: A total of 167 stillbirth were identified among 10,733 cases of total delivery during the study period, indicating that the incidence of stillbirth was 1.6%. Stillbirth in Group 1 account 42.9% among all cases. The proportion of the unknown cause rises with advancing GA. Preterm premature rupture of membrane was the major cause of early stillbirth. Acute chorioamnionitis or funisitis of higher stages were observed at an earlier GA. Similar patterns were seen in chronic inflammatory and fetal vascular thrombo-occlusive findings. However, findings of maternal under-perfusion show a stronger correlation with higher GA. Conclusion: The cause of stillbirth in earlier GA is associated with inflammation of placenta, whereas stillbirth in advanced GA is associated with maternal under-perfusion of placenta.