Background Stillbirth often remains unexplained, mostly due to a lack of any postmortem examination or one that is incomplete and misinterpreted. Materials and methods This retrospective cohort study was conducted at the Department of Obstetrics and Gynecology, Helsinki University Hospital, Finland, and comprised 214 antepartum singleton stillbirths from 2003 to 2015. Maternal and fetal characteristics and the results of the systematic postmortem examination protocol were collected from medical records. Causes of death were divided into 10 specific categories. Re-evaluation of the postmortem examination results followed. Results Based on our systematic protocol, the cause of death was originally defined and reported as such to parents in 133 (62.1%) cases. Re-evaluation of the postmortem examination results revealed the cause of death in an additional 43 (20.1%) cases, with only 23 (10.7%) cases remaining truly unexplained. The most common cause of stillbirth was placental insufficiency in 56 (26.2%) cases. A higher proportion of stillbirths that occurred at ≥39 gestational weeks remained unexplained compared to those that occurred earlier (24.1% vs. 8.6%) (P = 0.02). Conclusion A standardized postmortem examination and a re-evaluation of the results reduced the rate of unexplained stillbirth. Better knowledge of causes of death may have a major impact on the follow-up and outcome of subsequent pregnancies. Also, closer examination and better interpretation of postmortem findings is time-consuming but well worth the effort in order to provide better counseling for the grieving parents.