Methodology to study the volume and absolute placental density in human placenta at term - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: to compare two methodologies for the calculation of placental volume in normal term pregnancies: one according to the Archimedes principle and the other to the cylinder volume, to estimate the absolute placental densities. Also, to define the methodology which relates to the weight and to the newborn classification. METHOD: fifty placentas from normal term pregnancies were tested by the two methodologies to estimate the placental volume and absolute density: a) Archimedes principle, and b) the cylinder volume with two possible different heights. The absolute placental densities were calculated, respectively, by the quotient between the placenta weight, properly standardized, and the different estimated volumes. RESULTS: most of the pregnant women had more than one gestation, average age of 25.4 years, mean placental volume between 547.8 and 610 cm³ and mean density between 0.94 and 1.14 g/cm³, depending on the used methodology. CONCLUSIONS: the Archimedes principle was the most appropriate methodology to estimate the term placental volume, best correlating with the newborn weight, the placental index and the classification of newborn weight in relation to gestational age.