The present study has investigated the causes of weight deficit at birth, emphasizing the interaction between social, economical, cultural and environmental variables, as the Low Weighted Birth (LWB) determining factors. The population studied comprised 371 mothers and their live newborn non-twinned children, whose births had occurred in a Manaus public maternity hospital from September 1998 to May 1999. The predominance of Adequately Weighing of Recently Born Children was 69,5%, whereas 8,9% and 21,6% of the children were in the low and not enough weight categories, respectively. Young age, short height and low educational status were recorded as the mothers' main characteristics. The analysis of the results allowed us to conclude that the occurrence of weight deficit of children at birth is high in Manaus, and that mothers' low level of education, teenage pregnancy, fathers' absence, and precarious mother-child welfare care, probably a result from badly managed pre-natal welfare planing, are amongst the most important determining factors. The family's low income was also worsened by the occurrence of high numbers of members, which reduces the intra-familiar food purchasing power.
birth weight; determining factors; mother-child welfare care