A Placental Cause of Intra-uterine Fetal Death Depends on the Perinatal Mortality Classification System Used

Different classification systems for the cause of intra-uterine fetal death (IUFD) are used internationally. About two thirds of these deaths are reported as unexplained and placental causes are often not addressed. Differences between systems could have consequences for the validity of vital statistics, for targeting preventive strategies and for counselling parents on recurrence risks. Our objective was to compare use of the Tulip classification with other currently used classification systems for causes of IUFD. We selected the extended Wigglesworth classification, modified Aberdeen and the classifications by Hey, Hovatta, de Galan-Roosen and Morrison. We also selected the ReCoDe system for relevant conditions, comparable to contributing factors in the Tulip classification. Panel classification for 485 IUFD cases in the different systems was performed by assessors after individual investigation of structured patient information. Distribution of cases into cause of death groups for the different systems varied, most of all for the placental and unknown groups. Systems with a high percentage of cases with an unknown cause of death and death groups consisting of clinical manifestations only are not discriminatory. Our largest cause of death group was placental pathology and classification systems without placental cause of death groups or minimal subdivision of this group are not useful in modern perinatal audit as loss of information occurs. The most frequent contributing factor was growth restriction. This illustrates the vital role of the placenta in determination of optimal fetal development. In the Tulip classification, mother, fetus and placenta are addressed together. The system has a clear defined subclassification of the placenta group, a low percentage of unknown causes and is easily applied by a multidisciplinary team. A useful classification aids future research into placental causes of IUFD.