Abstract
Purpose :
Low birth weight and gestational age are two of the most important risk factors for developing retinopathy of prematurity (ROP). Slow postnatal weight gain is also strongly associated with ROP. High altitude remains an important determinant of increased low birth weight rates in places such as Colorado, USA. The purpose of this study was to investigate whether maternal residence at high altitude alters the risk for ROP in premature infants.
Methods :
This was a retrospective cohort study comparing elevation associated with the mother’s residential zip code and rates of ROP in premature infants in a well characterized ROP registry cohort at a tertiary care facility in Colorado between January 2006 and December 2020. All infants in the study had a gestational age less than 31 weeks, birth weight less than 1500 grams, or an unstable clinical course according to current guidelines, as well as available maternal residential zip code information. Geocoding was performed in SAS by adding a latitude and longitude for the geographic center of each zip code. Coordinates for each zip code were exported and entered into https://apps.nationalmap.gov/elevation to obtain elevation. The resulting file was merged with the ROP registry dataset based on zip code.
Results :
1817 infants were included in the cohort, with 318 unique zip codes with associated elevation data (Figure 1). Elevation ranged from 0 to 10,000 ft, with the majority of births associated with elevations 4,000 - 7,000 ft. Higher elevation was associated with lower birth weight percentiles, higher gestational age and maternal age at delivery. These associations were similar when evaluating data specifically between 4,000 and 8,000 ft. Figure 2 demonstrates the nonsignificant distribution of ROP type by elevation. Severe ROP (type 1 or type 2) developed in 10.2% of infants (186/1817); there was no significant association between ROP and elevation after adjusting for gestational age, birth weight percentile and maternal age (p=0.25).
Conclusions :
Despite the known increased rates of low birth weight in babies born to mothers living at high altitude, we found no significant association between altitude and ROP in premature infants in our cohort.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.