Reference Values for Placental Weight and Placental:Fetal Weight Ratio in a Swedish Population

Introduction: There is important clinical information from placental weight and its ratio to the fetal weight. The aim with this study was to establish reference values for the placental weight and the placental:fetal weight ratio for gestational weeks 13-43 in a Swedish population. Materials and Methods: Cases were retrospectively collected from the database used at the Pathology Department at Karolinska University Hospital and information about the placental weight, fetal weight, and gestational age was retrieved. Conditions, which could affect the placental- or fetal weight were excluded. Thereafter percentile curves were calculated for the placental weight and the placental:fetal weight ratio for gestational weeks. Results: A total of 730 cases were included and percentile curves for the placental weight for gestational week 13-43 and placental:fetal weight ratio for gestational week 18-43 are presented. Conclusions: Reference values for post fixation placental weight and its ratio to fetal weight for a Swedish population are presented. The reference values are lower than the current reference values used in our institution, and this will be of importance when interpreting findings after placental examination.