Scientists from the School of Public Health have found that exclusive breast-feeding is best for low-birth-weight infants during the first six months of life. Studies conducted in Bangladesh show that if exclusively breast-fed, babies born small at birth 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 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, an associate professor in the Department of International 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 1993-95. Each baby's weight and length were measured at enrollment and again in follow-up visits during the first year at 1, 3, 6, 9 and 12 months. Information also was collected on feeding and illness since birth. Almost half of the newborns (46.4 percent) were low-birth-weight (under 2,500 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 breast-fed at 1 month of age, a figure that declined to about a quarter of the infants by 3 months.
All other factors remaining constant, infants who were exclusively breast-fed in the first three months were on average about 95 grams heavier and 0.5 centimeters taller at 12 months than those breast-fed partially or not at all. In addition, the investigation showed that foods and fluids other than breast milk, if given before age 6 months, had an independent negative effect on the weight and length an infant would attain. "This," Baqui said, "further strengthens the argument that complementary foods before 6 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 6 months of age.
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 breast-feeding's sustained effect on growth and its even more beneficial effect in lighter infants were compelling reasons for promoting exclusive breast-feeding in early infancy.
Support for the study was provided by the U.S. Agency for International Development, the Center for Health and Population Research at Johns Hopkins and the Royal Netherlands Government.