Effect of gestational age on cord blood plasma copper, zinc, magnesium and albumin.

Background: The transport of essential trace elements from mother to fetus varies throughout gestation, and the role of transport proteins in the neonate and the mother may change during pregnancy. Magnesium, often used as tocolytic agent, may reach the fetus and appear in cord blood at higher than normal concentrations.

Aims: To determine cord blood plasma zinc, copper and magnesium concentrations, as well as plasma albumin in premature and full-term newborns, and correlate these values with those of maternal blood plasma at birth. Also, to examine whether cord blood plasma concentration of these elements varies with gestational age.

Subjects: The 35 mother-infant pairs included: 11 in the 38-42-week gestational age (GA), 9 in the 34-37-week GA, 11 in the 29-33-week GA group and 4 in the 24-28-week GA. Magnesium for tocolysis was given to five of the mothers in the 29-33-week GA cohort and two of the women giving birth at 24-28-week GA.

Results: Trend analysis showed that while cord plasma zinc decreased with GA at birth, the reverse was observed for copper. There were no differences with GA either in maternal plasma zinc or copper. However, maternal ceruloplasmin tended to decrease with GA (P=0.0174). Maternal and cord blood plasma magnesium exhibited a strong correlation (r=0.942, P<0.001), as well as between cord plasma magnesium and zinc (r=0.448, P<0.01).

Conclusions: While the vigorous mother-to-fetus uphill zinc transfer is clear throughout the last trimester, copper remains in cord blood plasma at much lower concentrations than in the mother, suggesting that prematurity may place the newborn infant at a greater risk than the term infant to copper deficiency. This situation, together with a reduced synthesis in the fetus of the transport protein ceruloplasmin, creates another potential challenge in the nutritional support of the premature infant.