The Effect of Altitude on Birthweight/Length Ratio: A Population-Based Study Over 36 Years in an Altitude Range from Sea Level to 1,700 m
Bibliographic record
Abstract
Klebermass-Schrehof Katrin, Thomas Waldhoer, and Lin Yang. The effect of altitude on birthweight/length ratio: a population-based study over 36 years in an altitude range from sea level to 1,700 m. High Alt Med Biol . 23:90–95, 2022. Objective: The negative effect of altitude on fetal growth has been documented, but it is unknown whether this effect changes over time. We investigated the effect of altitude on infant birthweight/length ratio as well as its potential dependence on gestational age and year of birth in the range from sea level up to 1,700 m (Austria). Materials and Methods: Data on maternal characteristics, infant birthweights, and infant lengths were extracted from all Austrian birth certificates between 1984 and 2019. Results: A total of 2,240,439 birth certificates were identified and analyzed. The effect of altitude on birthweight/length ratio was −2.66 g/cm (95% confidence interval [CI]: −2.77 to −2. 54) per 1,000 m increased altitude in 1984–1986, which decreased to −1.96 g/cm (95% CI: −2.09 to −1.82) in 2017–2019. The effect of altitude on birthweight/length ratio remained constant for preterm infants, which fluctuated around −1.5 g/cm. For term infants, the negative effect of altitude on birthweight/length ratio attenuated from −3 to −1.9 g/cm over time with a stronger decrease for infants born between 41 and 42 compared with those between 37 and 40 weeks of gestation. Conclusion: In summary, our data demonstrate a strong effect of altitude on birthweight/length ratio over 36 years with a smaller effect in recent years and a stronger effect in infants born around term age compared with preterm infants.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".