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Prenatal Zinc May Impair Infant Mental Development
Lancet
07/25/2002
By Harvey McConnell
Providing zinc supplementation to pregnant women in countries where diet is deficient could impair the early mental development of their infants.
This unexpected finding prompts researchers to urge caution about using zinc supplements among pregnant women. This advice is allied with a call for a new look in providing supplementation in developing countries by Drs Sally McGregor and Jena Habadani from the Institute for Child Health, London, England, and colleagues from the International Center for Diarrhoeal Disease Research, Bangladesh.
The findings place clinicians in a conundrum and complicate future policy. Previous trials showed zinc supplementation in infants has a beneficial effect on growth and morbidity, and supplementation in pregnant women is associated with reduced morbidity in low birthweight infants. Zinc deficiency is common in developing countries due to a diet that is low in animal protein and high in fibre.
Researchers in the ongoing study randomly assigned a cohort of 559 pregnant women to zinc (30 mg daily) or placebo from four months' gestation to delivery. They then assessed effects of zinc supplementation on pregnancy outcome, and on infant growth and morbidity in their first six months.
When the infants were 13 months old, the researchers randomly selected 168 infants from 383 who completed the study at six months. Then they assessed mental development with two scale programs, and measured weight and height.
Infants in the placebo group had higher scores for both mental and psychomotor development. Zinc supplementation had no significant effect on behaviour or growth. The children's nutritional status was poor--weight-for-age at testing was strongly related to development.
Dr McGregor and colleagues said that undernutrition is generally accepted to be detrimental to children's development, and their findings emphasize the serious nature of the problem in populations with high proportions of underweight children.
They conclude that undernourished pregnant women obviously require more than zinc alone. "The next step would be to examine the effect of more comprehensive supplementations to improve maternal nutritional status during pregnancy on a broad range of outcomes including infants' development."
Lancet 2002; 360: 290-94.
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