摘要：Scienti c Background: In developing countries, higher infant mortality is
partially caused by poor maternal and fetal nutrition. Clinical trials of micronutri-
ent supplementation are aimed at reducing the risk of infant mortality by increas-
ing birth weight. Because infant mortality is greatest among the low birth weight
infants (LBW) ( 2500 grams), an e
ective intervention may need to increase
birth weight among the smallest babies. Although it has been demonstrated that
supplementation increases the birth weight in a trial conducted in Nepal, there
is inconclusive evidence that the supplementation improves their survival. It has
been hypothesized that a potential bene t of the treatment on survival among
the LBW infants is partly compensated by a null or even harmful e
ect among
the largest infants. Exploratory analyses have suggested that the treatment e
ect
on birth weight might vary with respect to the percentiles of the birth weight
distribution.
