A prospective study of serial maternal serum zinc levels and pregnancy outcome.

A prospective study of 878 pregnant women in Adelaide, South Australia, examined the relationship of maternal serum zinc concentration to pregnancy outcome. Blood samples were obtained at weeks 18 and 32 of pregnancy, and from the umbilical cord. Additional detailed data were obtained, via standardised antenatal interview and review of clinical records, on antenatal care, personal, behavioural, and sociodemographic characteristics, and, subsequently, on delivery and neonatal assessment. Maternal mid-pregnancy zinc status was negatively correlated, although very weakly, with duration of gestation and with birthweight (including, in particular, the 18 recorded cases of intrauterine growth retardation). This finding accords with recent suggestions that, in non-experimental human studies in populations in which frank zinc deficiency is absent, maternal serum zinc level may be an outcome, rather than a determinant, of fetal growth later in pregnancy. Low mid-pregnancy zinc levels were associated with increased risk of intrapartum haemorrhage. In general, the greatest risk of having some complication or abnormality of delivery or neonatal functional status occurred in pregnant women who had both an initially below-average, and subsequently decreasing, serum zinc concentration. This corroborates other recent research. While it might be inferred that above-average fetal growth, by depressing maternal zinc status, could itself impair delivery and neonatal functioning, our data indicate that these effects operated independently.