Mother's milk and sewage: their interactive effects on infant mortality.

If they lived in households without piped water or a toilet, Malaysian infants who did not breast-feed were five times more likely to die after 1 week of age than those who breast-fed, when other significant factors affecting infant mortality were taken into account. This is double the relative risk associated with not breast-feeding for infants born into households with toilets, whether or not they had piped water. Analogously, improvements in toilet sanitation appear to have reduced mortality twice as much among infants who did not breast-feed as among those who did. These findings, from a retrospective survey of infants born to a probability sample of 1,262 women in peninsular Malaysia, confirm the pernicious synergistic effect of poor sanitation and nonbreastfeeding that was postulated previously on theoretical grounds. Promoting and maintaining high initiation of breast-feeding is thus particularly important where poor sanitation is prevalent. Even more affluent areas should not be neglected, however, because socioeconomic improvement, including improved environmental sanitation, is often accompanied by decreased breast-feeding. Although the risk to each nonbreast-fed infant was less in those areas, infants there were less likely to breast-feed in Malaysia, and hence they made up a significant proportion of lives that could be saved by breast-feeding.