Low zinc intake during pregnancy: its association with preterm and very preterm delivery

Zinc affects growth, development, and reproduction. However, the effect of poor maternal zinc nutriture, usually measured as plasma zinc, on poor pregnancy outcome has not been consistent. The influence of dietary zinc on pregnancy outcome was examined in a cohort of 818 pregnant girls and women from a poor urban community in Camden, New Jersey (1985-1990). Zinc intake in this sample was 11.1 mg/day, a level ascertained from averaged 24-hour dietary recalls during pregnancy. Gravidas with low zinc intake (< or = 6 mg/day, amounting to 40% of the recommended dietary allowance for pregnancy) had lower caloric intake and multivitamin usage as well as a higher incidence of inadequate weight gain during pregnancy and iron deficiency anemia at entry to prenatal care compared with those with higher intakes. A low zinc intake was associated with approximately a twofold increase in the risk of low birth weight (< 2,500 g) after controlling for calories and other confounding variables. The risk of preterm delivery (< 37 completed weeks) was also increased, particularly when rupture of the membranes preceded the onset of labor (adjusted odds ratio = 3.46, 95% confidence interval 1.04-11.47). A low intake of dietary zinc earlier in pregnancy was associated with a greater than threefold increase in the risk of very preterm delivery (< 33 completed weeks). In conjunction with iron deficiency anemia at entry to prenatal care, the adjusted odds ratio for very preterm delivery with low zinc intake was 5.44 (95% confidence interval 1.58-18.79). Among the urban poor, a marginal zinc intake during pregnancy may play an important role in the duration of gestation and is associated with increased risk of preterm and very preterm delivery.