Altitude and risk of pre-eclampsia: insights from a large-scale epidemiological study in Ecuador.

Exposure to hypobaric hypoxia at high altitude is associated with adverse pregnancy outcomes, including low birth weight and stillbirth. However, the relationship between high altitude and pre-eclampsia remains less well defined, with conflicting findings in previous studies. Improved understanding of pre-eclampsia risk at altitude could help in targeting resources, particularly in low-resourced settings. This study aimed to evaluate the impact of altitude, analysed as a continuous nonlinear variable, on the risk of pre-eclampsia in Ecuador. Publicly available maternal health records from Ecuador (2021-23) were obtained from the National Institute of Statistics and Census. Geospatial techniques were used to assign the altitude of maternal residence, and generalized additive models determined the relationship between altitude and pre-eclampsia incidence, adjusting for maternal age, ethnicity, healthcare access, and residence. Models were fitted using restricted maximum likelihood. After adjusting for confounders, no significant increase in pre-eclampsia risk was observed with higher altitude. However, as expected, increased risk was noted at the extremes of maternal age (p <0.001) and among women with publicly funded care (p <0.001). Ethnicity was also a risk determinant, but no interaction with altitude was found. Comparison of our findings with population-wide studies elsewhere is a key future goal.This article is part of the discussion meeting issue 'Pregnancy at high altitude: the challenge of hypoxia'.