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Zinc blood levels during pregnancy don't seem to affect pregnancy complications or neonatal outcomes

Zinc deficiency during pregnancy in experimental animals causes fetal growth retardation and malformations. A firm consensus has never been reached about the impact of zinc intake during human pregnancy and its impact on pregnancy, delivery, and neonatal outcomes. However, the largest study to date found no relationship between blood zinc levels and pregnancy outcomes. The study was conducted by the Patient Outcomes Research Team (PORT) on Prevention of Low Birthweight in Minority and High-Risk Women and supported in part by the Agency for Healthcare Research and Quality (PORT contract no. 290-92-0055).

Led by PORT principal investigator Robert L. Goldenberg, M.D., of the University of Alabama at Birmingham, the researchers measured zinc concentrations in plasma samples at a mean of 16 weeks gestation from 3,448 women attending a public health clinic for their prenatal care; 85 percent of the women were black, and 15 percent were white. They ranged in age from 11 to 44 years, with a mean age of 22.4.

After adjustments were made for gestational age, plasma zinc concentrations were not significantly associated with any measure of pregnancy outcome or neonatal condition. For example, the researchers found no significant differences in the prevalence of maternal complications among women with the lowest and the highest plasma zinc concentrations. Nor were there any significant differences in the groups in the prevalence of fetal growth restriction, preterm delivery (less than 37 weeks), early preterm delivery (less than 32 weeks gestation), hypertension, amnionitis, or postpartum infections.

In addition, there were no significant correlations between plasma zinc scores and various neonatal measures such as birth weight, head circumference, Apgar scores at 1 and 5 minutes, gestational age at birth, and crown-heel length. This study agrees with the findings of about half of previous studies that found no relationship between zinc concentration and pregnancy outcome, and it disagrees with the other half of studies that did find some positive association. However, this study was the largest one to date; the other studies involved fewer than 1,000 women.

See "Maternal plasma zinc concentrations and pregnancy outcome," by Tsunenobu Tamura, M.D., Dr. Goldenberg, Kelley E. Johnston, B.A., and Mary DuBard, B.A., in the January 2000 American Journal of Clinical Nutrition 71, pp. 109-113.

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