Updating reference values for placental weights in Northern Alberta

The purpose of this study was to establish normal parameters for placental weights and fetal/placental weight ratios. Placentas (2402) from uncomplicated singleton deliveries at the Royal Alexandra Hospital (Edmonton, Alberta) were collected from 1997 to 1998 and weighed after fixation. The nonparametric Mann-Whitney test was applied. New reference values were developed for fixed placental weights. Placentas at the 90th percentile were 50 to 100 g heavier than previously reported. Fetal/placental weight ratios at term were similar to published values. The new placental weight reference values from our institution represent a recent and local population. New values may partly reflect parallel increases in term birth weights.