Placental zinc in normal and intra-uterine growth-retarded pregnancies

The zinc concentration of placental tissue and cord blood in sixteen mothers who gave birth to normal babies was measured. The blood volume of each placenta was estimated from measurements of haemoglobin concentration of placental homogenate and cord blood, and, by deduction, the Zn content of blood-free placental tissue was calculated. Results were compared with eleven mothers whose fetuses showed a low biparietal diameter velocity between 17 and 28 weeks gestation and with ten mothers who gave birth to intra-uterine growth-retarded (IUGR) babies. As expected, placental weight was significantly correlated with infant birth weight. Blood-free placental tissue contained about four times more Zn (approximately 10 micrograms Zn/g) than cord blood (approximately 2.5 micrograms Zn/ml). Concentrations of Zn in blood-free placental tissue were similar in all three groups, but the cord blood Zn of mothers producing IUGR babies was significantly lower than that of the other two groups. Results of the present study suggested that fetal growth retardation in the mothers studied could not be explained by differences in blood-free placental Zn concentration, but that there may be some association between lower cord blood Zn levels and intra-uterine growth retardation.