Abstract
To understand the relationship between birth weight and altitude to improve health outcomes in high-altitude populations, to systematically assess the impact of altitude on the likelihood of low birth weight (LBW), small for gestational age (SGA), and spontaneous preterm birth (sPTB), and to estimate the magnitude of reduced birth weight associated with altitude. PubMed, OvidEMBASE, Cochrane Library, Medline, Web of Science, and clinicaltrials.gov were searched (from inception to November 11, 2020). Observational, cohort, or case-control studies were included if they reported a high altitude (>2500m) and appropriate control population. Of 2524studies identified, 59 were included (n=1604770 pregnancies). Data were abstracted according to PRISMA guidelines, and were pooled using random-effects models. There are greater odds of LBW (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.33-1.62, P<0.001), SGA (OR 1.88, 95% CI 1.08-3.28, P=0.026), and sPTB (OR 1.23, 95% CI 1.04-1.47, P=0.016) in high- versus low-altitude pregnancies. Birth weight decreases by 54.7g (±13.0g, P<0.0001) per 1000 m increase in altitude. Average gestational age at delivery was not significantly different. Globally, the likelihood of adverse perinatal outcomes, including LBW, SGA, and sPTB, increases in high-altitude pregnancies. There is an inverse relationship between birth weight and altitude. These findings have important implications for the increasing global population living at altitudes above 2500m.
Highlights
Pregnancy at high altitudes (>2500 m) involves the physiological challenge of adapting to pregnancy with altered physiology from environmental hypobaric hypoxia
Term infants born at high altitudes were on average 307 g lighter (Figure S6) than those born at low altitudes
There was no significant difference in gestational age between infants born at high altitudes versus those born at low altitudes (Figure 6)
Summary
Pregnancy at high altitudes (>2500 m) involves the physiological challenge of adapting to pregnancy with altered physiology from environmental hypobaric hypoxia. |2 with short-and long-term adverse health outcomes, including increased risk of neonatal death,[12] childhood stunting,[13] and increased risk of obesity[14] and cardiovascular disease later in life.[15,16] Studies suggest higher rates of pregnancy complications associated with reduced birth weight in high-altitude populations, including stillbirth,[10] pre-eclampsia,[7] and gestational hypertension.[11,17] estimates of the impact of altitude on pregnancy vary widely across global contexts,[4,5,7] with some studies finding no significant impact.[18,19]. A screening of titles and abstracts was performed, followed by an in-depth full-text analysis (Figure S1)
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