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Birth weight and altitude: a study in Peruvian communities
J P Mortola1, P B Frappell, L Aguero
1Department of Physiology, McGill University, Montreal, Quebec, Canada.
Insights
High altitude significantly impacts birth weight, with a notable decrease observed above 2000 meters. This decline in infant weight is directly related to altitude and barometric pressure, not socioeconomic status.
Area of Science:
- Altitude research
- Human physiology
- Perinatal health
Background:
- High altitude environments present unique physiological challenges.
- Understanding factors affecting birth weight is crucial for infant health.
- Previous studies suggest altitude may influence fetal growth.
Purpose of the Study:
- To test the hypothesis that birth weight decreases at high altitude.
- To identify the critical altitude and barometric pressure threshold for this effect.
- To determine the relationship between altitude and birth weight decline.
Main Methods:
- Collected birth weight data from 15 centers in Peru (sea level to 4575 m).
- Analyzed data covering a 1-year period (November 1997 to October 1998).
- Correlated birth weight with altitude and barometric pressure (Pb).
Main Results:
- Birth weight declined significantly above approximately 2000 m altitude (Pb < 590 mm Hg).
- A decrease of 65 g per 500 m increase in altitude was observed.
- This pattern was consistent across sexes and socioeconomic groups.
Conclusions:
- A critical barometric pressure threshold (approx. 590 mm Hg) triggers reduced birth weight.
- The reduction in birth weight is proportional to altitude between 2000 m and 4500 m.
- Socioeconomic factors do not influence the altitude-related drop in birth weight.
Abstract:
We tested the hypothesis that at high altitude birth weight decreases once a critical barometric pressure (Pb) is reached. Birth weight data covering the 1-year period from November 1997 to October 1998 were collected in Peru from the data files of 15 community and mining centers between sea level and 4575 m altitude. These centers are scattered along the main road that joins Lima (on the Pacific shore) to Cerro de Pasco (4330 m) and surroundings. Above approximately 2000 m (ie, at Pb below approximately 590 mm Hg, inspired O(2) partial pressure of approximately 114 mm Hg) and up to approximately 4500 m altitude birth weight declined at an average of 65 g for every additional 500 m altitude (or 105 g for every additional 50 mm Hg drop in Pb). This pattern did not differ between sexes. Averages and modal distributions of the birth weight from 2 hospitals in Cerro de Pasco (4330 m) serving different social groups were similar. Body length at birth was similar at various altitudes, with the exception of the 2 highest locations above 4500 m, where it was slightly reduced. From these data, together with additional data collected in the North of Peru (Chacas, 3360 m) and with results from other ethnic groups previously published, we conclude that the drop in birth weight at altitude is (1) apparent once the critical Pb of approximately 590 mm Hg is reached, corresponding to an altitude of approximately 2000 m, (2) proportional to the increase in altitude between approximately 2000 m and 4500 m, and (3) independent from socioeconomic factors.