Effects of altitude versus economic status on birth weight and body shape at birth

The compelling evidence linking small size at birth with later cardiovascul ar disease has renewed and amplified a clinical and scientific interest in the determinants of fetal growth. Although the effects of maternal nutritio n on fetal growth have been extensively studied, comparatively little is kn own about the effects of maternofetal hypoxia. This study tested the hypoth esis that in highland regions, high altitude rather than maternal economic status is associated with reduced and altered fetal growth by investigating the effects of high altitude versus economic status on birth weight and bo dy shape at birth in Bolivia. Bolivia is geographically and socioeconomical ly unique. It contains several highland (>3500 m above sea level) and lowla nd (<500 m) cities that are inhabited by very economically divergent popula tions. Birth weight, body length, and head circumference were compared betw een a high- (n = 100) and low- (n = 100) income region of La Pat (3649 m; l argest high-altitude city) and a high- (n = 100) and low- (n = 100) income region of Santa Cruz (437 m; largest low-altitude city). In addition, the f requency distribution across the continuum of birth weights was plotted for babies born from high- and low-income families in La Pat and Santa Cruz. M ean birth wrights were lower in babies from La Pat than in babies from Sant a Cruz in both high- and low-income groups. The cumulative frequency curve across all compiled birth weights was shifted to the left in babies from La Pat compared with those from Santa Cruz, regardless of economic status. Th e frequency of low birth weight (<2500 g) was higher in babies from La Pat than from Santa Cruz in both high- and low-income groups. In addition, at h igh altitude but not at low altitude, high income was associated with an in crease in the head circumference:birth weight ratio. These findings suggest that high altitude rather than economic status is associated with low birt h weight and altered body shape at birth in babies from Bolivia.