Graduated effects of high-altitude hypoxia and highland ancestry on birth size

BACKGROUND: We present a cohort of ca. 25,000 birth records from Bolivia of men and women who are currently adults. We used this cohort to test the hypothesis that high altitude reduces birth weight and that highland ancestry confers graduated protection against this effect. METHODS: Birth records were obtained from obstetric clinics and hospitals in La Paz (3,600 m) and Santa Cruz (420 m). Only singleton, healthy term (> 37 wk) pregnancies of nonsmoking mothers were included. Andean, Mestizo, or European ancestry was determined by validated analysis of parental surnames. RESULTS: High altitude reduced body weight (3,396 +/- 3 vs. 3,090 +/- 6 g) and length (50.8 +/- 0 vs. 48.7 +/- 0 cm) at birth (P < 0.001). Highland ancestry partially protected against the effects of high altitude on birth weight (Andean = 3,148 +/- 15 g; Mestizo = 3,081 +/- 6 g; and European = 2,957 +/- 32 g; trend P < 0.001) but not on birth length. The effects of high-altitude pregnancy on birth size were similar for male and female babies. CONCLUSION: High altitude reduces birth weight and highland native ancestry confers graduated protection. Given previous studies linking reduced birth weight with increased risk of cardiovascular disease, further study is warranted to test whether adults from high-altitude pregnancy are at increased risk of developing cardiovascular disease.