Secular trend in neonatal mortality in the moutain states

Reviewing trends in neonatal mortality from 1957 to 1967, it is clear that neonatal and infant mortality has declined faster in the mountain states than in the low altitude states. Accordingly, the increased neonatal and infant mortality at high altitudes or in the mountain states cannot be attributed to high altitude hypoxia alone. Furthermore, the decline in neonatal mortality in the mountain states has not been accompanied by a decrease in the frequency of low birth weight (below 2500 gm) and is therefore not a product of increasing body size in the neonate.     

Developmental responses to high altitude hypoxia

From a review of published literature on developmental responses to high altitude, three major conclusions are derived. First, the small birth weight of high altitude native populations are adaptive responses to reduce the oxygen requirements, while the relative increase in the placental weight is a compromise mechanism to increase the volume and surface area for a better oxygenation. Second, the small stature of the high altitude native is due to slow prenatal and postnatal growth. Third, the enlarged chest size, increased lung volumes and predominance of the right ventricle of the heart are due to accelerated development during childhood and adolescence. However, there is not adequate information to determine whether or not the developmental responses of the high altitude native are population-specific, based on a genetic structure different from that of sea level populations. Hence, the need for further study of developmental factors is emphasized.     

Developmental and nutritional determinants of pregnancy outcome among teenagers

To investigate the determinants of low birth weight in infants born to adolescent mothers, we studied the obstetric population attended at the Maternity Hospital of Lima, Peru. From this population, 1256 gravidas, ranging in age from 12 to 25 years, volunteered to participate in this study. Anthropometric and biochemical measurements were used to evaluate the nutritional status and physiological maturity of the mother and newborn. For analytical reasons the young teenaged mothers (less than 15 years) were classified as either still-growing or having completed their growth, depending on their height relative to their parents' height. Similarly, the young teenagers were classified as either gynecologically immature or gynecologically mature depending on whether their gynecological age was less than or greater than 2 years. Our results indicate that young still-growing teenagers, even when matched for nutritional status, have smaller newborns than adult mothers. The data also demonstrate that maternal gynecological age per se does not affect prenatal growth. As inferred from multivariate analyses, it appears that the reduction in birth weight among young teenagers can be explained in part by a decreased net availability of nutrients resulting from the competition for nutrients between the mother's growth needs and the growth needs of her fetus and by an inability of the teenage placenta to maintain placental function adequately for active fetal growth.     

Childhood retardation resulting in reduction of adult body size due to lesser adolescent skeletal delay

The skeletal maturation of 7972 rural children from the six Central American nations, aged one month through 22 years, is evaluated. The results suggest that retardation in skeletal maturation during childhood is significantly greater than during adolescence, while growth in body size shows a progressive delay from infancy through adolescence. In other words, the apparent improvement in skeletal maturation during adolescence is not associated with an equivalent “catch-up” in body size. Similarly, prolongation of the period of growth does not fully compensate for the slow rate of growth. It is postulated that the small stature in Central America is related to the marked childhood retardation and to the fact that during adolescence, the timing of skeletal maturation is less affected than growth in size.     

Altitude and growth: a study of the patterns of physical growth of a high altitude Peruvian Quechua population

Data on physical growth were obtained for a sample of 1202 Quechua subjects, aged 2 to 35 years from the district of Nuñoa, Puno, located in the southern highlands (altitude 4000–5500m) of Peru. These data were supplemented by a three-year longitudinal study of 300 subjects, aged 1 to 22 years. The patterns of physical growth of members of the indigenous population of Nuñoa are characterized by (1) late sexual dimorphism, (2) slow and prolonged growth in body size, (3) late and poorly defined adolescent stature spurt in both males and females, and (4) accelerated development in chest size. The socio-economic factors associated with urban-rural and altitude differences appear to be reflected in greater deposition of subcutaneous fat and increased weight but do not seem to influence the development of stature. We suggest the pattern of growth of this population is related to the hypoxic effects of high altitude, and/or reflects a genetic adaptation to such stress. The anthropometric and physiological studies conducted during this and previous studies and the comparative data from Peruvian populations situated at lower altitudes document the specific adaptive response of the chest wall to the hypoxic effects of high altitude.