It has not been determined whether the concentration of essential elements in the meconium of dizygotic twins is indistinguishable or is related to birth weight or placental size differences. We hypothesized that dizygotic twins of discordant size would have a dissimilar concentration of essential elements in the meconium, whereas concordant twins would not exhibit such a difference. We also hypothesized that the smaller the infant/placental weight ratio, the greater the concentration of essential elements in meconium. This study was aimed at verifying these hypotheses. Twenty-six pairs of dizygotic twins, regardless of sex, were divided into two groups separated by the median value of weight discrepancy (13.1%) into concordant (CC) ี
13.1% and discordant (DC) >13.1%. The concentrations of seven essential elements (calcium, magnesium, phosphorus, copper, zinc, iron, and manganese) were measured in the meconium. Total placental weights for all twins were also correlated with infant weights and meconium element concentration. Heavy/light birth weight ratio of the DC, but not of CC twins, corresponded to a meconium concentration ratio >1 for calcium, magnesium, iron, zinc, and manganese, but not for phosphorus and copper. There was a strong correlation between total twin weight and total placental weight for both the CC and DC groups. However, infant/placental weight ratio did not correlate with meconium element concentration. It may be inferred that in dizygotic twins, a higher essential element concentration in meconium may reflect the greater access of the heavier fetus to maternally supplied nutrients, or a different functional capacity of the gastrointestinal tract.