Summary of Findings: The Problem of Low Birth Weight

  • Although reliable data on the magnitude and global distribution of low birth weight (LBW) are limited, it is estimated that approximately 16 percent of all neonates in developing countries weigh less than 2,500 grams at birth and that more than 20 million such infants are born each year.

  • LBW may result from intrauterine growth restriction (IUGR) or preterm delivery. In developing countries, gestational age is frequently not known, which makes it difficult to distinguish between these two conditions. Nonetheless, most LBW in developing countries appears to be disproportionately due to high rates of IUGR, rather than preterm birth. Current interventions are more effective for IUGR than preterm birth.

  • The least-developed countries have the highest rates of infant mortality and the highest rates of LBW. Since countries have been more successful in reducing infant mortality than LBW, future efforts should focus on reducing mortality in all neonates and infants regardless of their weight.

  • Poor nutritional status is the principal cause of IUGR in developing countries. Although clinical trials have shown that increasing the food intake of pregnant women increases fetal growth, public health programs on larger populations of women have not been more than minimally effective in reducing IUGR. Malaria prophylaxis and intensive smoking cessation programs have been effective in reducing IUGR.

  • For preterm birth, the leading causes are genitourinary infection, multiple birth, pregnancy-induced hypertension, and low prepregnancy weight. Additional risk factors include malaria and cigarette smoking. Antibiotic treatments of pregnant women appear to be effective for asymptomatic bacteriuria, are not clearly effective for bacterial vaginosis, and are not effective for trichomoniasis or chlamydia. Antihypertensive treatment has not been effictive in lowering the risks of IUGR or preterm birth. Malaria prophylaxis, intensive counseling on smoking cessation, and fish oil supplementation are effective. Where resources permit, women with documented cervical incompetence may benefit from a cerclage procedure.

  • Two strategies for reducing neonatal and infant mortality among LBW infants that do not depend on expensive care or technology include breastfeeding and/ or use of expressed breast milk and Kangaroo mother care.



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