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March 1, 2001

Some Low-Birth-Weight Infants Destined to Be Small for Life

Scientists from the Johns Hopkins School of Public Health have found that exclusive breastfeeding is best for low-birth-weight infants during the first six months of life. Studies conducted in Bangladesh show that babies born small at birth, if exclusively breast-fed, had significantly better chances for catch-up growth compared to small infants given other fluids or foods during the first six months. The report appears in the March 2001 issue of the European Journal of Clinical Nutrition.

The study also found that the differences in weight and length between low-birth-weight infants and their heavier peers remained the same throughout the first year of life. This is in contrast to babies born in more developed countries, where pre-term and small infants usually grow faster and eventually catch-up to their heavier peers later in life.

Said senior author Abdullah Baqui, associate professor, International Health, Johns Hopkins School of Public Health, "Infants born in the slums of Dhaka appear to be confined within 'growth channels' determined at birth, so that bigger babies grew ever bigger relative to their smaller peers." Although shorter babies did appear to make up some of their shortfall in the first six months, the taller babies grew relatively even taller in the second six months of life.

The researchers observed a group of infants born in Dhaka from birth until age 12 months during 1993-1995. Each baby's weight and length were measured at enrollment and again during follow-up visits carried out at ages 1, 3, 6, 9, and 12 months. Information was also collected on feeding and illness since birth. Almost half of the newborns (46.4 percent) were low-birth-weight (under 2500 grams). Pre-term deliveries accounted for 17 percent of all infants, and almost 70 percent of the samples were small for gestational age. A little more than half of the infants were exclusively breastfed at one month of age, a figure that declined to about a quarter of the infants by three months.

All other factors remaining constant, infants who were exclusively breastfed in the first three months were on average about 95 grams heavier and 0.5 centimeters taller at 12 months than those partially or not breastfed. In addition, the investigation showed that foods and fluids other than breast milk, if given before age six months, had an independent negative effect on the weight and length an infant will attain. "This," said Dr. Baqui, "further strengthens the argument that complementary foods before six months of life are not necessary and are frequently detrimental."

The investigators also studied the effects of illness on growth. Diarrhea negatively affected both weight and length significantly in both newborns and those past six months of age. Acute respiratory infection had a significant negative association with weight but not length, and the size of this effect was larger in the older infants.

The authors emphasized that a better understanding of the role of nutritional status at birth in infant growth could help policy makers in developing countries to forge appropriate decisions about health programs. The scientists said that breastfeeding's sustained effect on growth and its even more beneficial effect in lighter infants were compelling reasons for promoting exclusive breastfeeding in early infancy. They hope their results will provide renewed impetus to the efforts for the promotion of breastfeeding, especially exclusive breastfeeding in the first six months of life.

Support for this study was provided by the U.S. Agency for International Development (USAID), the Center for Health and Population Research at the Johns Hopkins University, and the Royal Netherlands Government.

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