Low birth weight (LBW) has been defined by the World Health Organization (WHO) as weight at birth of less than 2.5 kg. The global prevalence of LBW is 15.5%, which amounts to about 20 million LBW infants born each year, 96.5% of them in developing countries.^I

LBW can be a consequence of preterm birth (before 37 completed weeks of gestation), small size for gestational age (SGA, defined as weight for gestation less than 10^th percentile), or a combination of both. Intrauterine growth retardation, defined as slower than normal velocity of fetal growth, is usually responsible for SGA. The term “LBW” thus includes a heterogeneous group of infants: some who are born early, some who are born at term but SGA, and some who are both born early and SGA.

Being born with LBW is generally recognized as a disadvantage for the infant. Preterm birth is a direct cause of 27% of the 4 million neonatal deaths that occur globally every year.^II Preterm birth and SGA are also important indirect causes of neonatal deaths. Directly or indirectly, LBW may contribute to

60% to 80% of all neonatal deaths.^II LBW infants are at higher risk of early growth retardation, infection, developmental delay and death during infancy and childhood.^III-IV

Countries can reduce their neonatal and infant mortality rates by improving the care of LBW infants. Experience from developed and low- and middle-income countries has clearly shown that appropriate care of LBW infants, including their feeding, temperature maintenance, hygienic cord and skin care, and early detection and treatment of problems such as infections can substantially reduce mortality. Interventions to improve feeding are likely to improve the immediate and longer-term health and

well-being of the individual infant and have a significant impact on neonatal and infant mortality at a population level. In the 1960s in the United Kingdom, better feeding was one of the first interventions for preterm babies that was associated with reduced case fatality in hospital settings before the advent of intensive care.^V Kangaroo Mother Care for LBW infants weighing less than 2 kg, which includes exclusive and frequent breastfeeding in addition to skin-to-skin contact and support for the mother- infant dyad, has been shown to reduce mortality in hospital-based studies in low- and middle-income countries.^VI Studies from India have shown that improved care of LBW infants in the community can be highly effective in improving their survival.^VII-VIII

LBW infants can be classified according to their gestation into term (born after 37 and before 42 completed weeks of gestation) and preterm (born up to 37 completed weeks of gestation). Infants in each of these categories can be further divided into two groups based on whether or not they are SGA. LBW infants are classified as very low birth weight (VLBW) if their birth weight is less than 1.5 kg, and as extremely low birth weight (ELBW) if their birth weight is less than 1 kg. Preterm infants of less than 32 weeks gestation are at greatest mortality risk, followed by preterm infants of 32-36 weeks gestation who are also SGA, preterm infants of 32-36 weeks gestation who are not SGA, and term

LBW infants. All these groups have a higher mortality risk than infants who do not have LBW.

WHO guidelines for feeding of LBW infants have not been available. The quality of care received by LBW infants in many low- and middle-income countries is inadequate. These infants are often not breastfed and many times not fed at all in the first hours and days of life. The objective of these

guidelines is to improve the quality of care received by LBW infants through improved capacity of the health workers who care for these infants.

These guidelines were developed using funding to the Department of Maternal, Newborn, Child and Adolescent Health from the United States Agency for International Development. The guidelines will be reviewed and updated in 2014, i.e. three years from the date of their publication.