The effect of Ambient heat exposure early in pregnancy on the frequency of congenital heart defects: A systematic review and meta-analysis
Bibliographic record
Abstract
INTRODUCTION: Congenital heart defects (CHD) is the most common birth defect worldwide and is associated with several maternal risk factors, such as obesity, diabetes, smoking, and advanced maternal age, as well as environmental exposures, including heat and air pollution. This systematic review aimed to evaluate the current evidence regarding the impact of maternal exposure to high ambient temperatures during pregnancy on the incidence of CHD in offspring. METHODS: We included comparative studies that directly assessed the relationship between high-temperature exposure during pregnancy and CHD. A comprehensive search of PubMed, Embase, Scopus, and Google Scholar was conducted on 11 December 2024. All eligible studies were assessed for methodological quality using the MINORS scale, and the risk of bias was evaluated using the Newcastle-Ottawa Scale. Study selection, data extraction, and risk of bias assessment were independently performed by two reviewers. The odds ratio (OR) was selected as the effect measure. A meta-analysis was conducted using Comprehensive Meta-Analysis Software (version 4), employing random-effects models to calculate pooled ORs with 95% confidence intervals (CIs). RESULTS: A total of 874 records were identified, and 14 studies were included in the final analysis. These included eight case-control and six cohort studies, predominantly conducted in the United States (n = 5) and China (n = 5). The meta-analysis revealed a statistically significant association between prenatal heat exposure and CHD, with a pooled OR of 1.079 (95% CI: 1.005-1.159). The 95% prediction interval ranged from 0.849 to 1.372. Subgroup analyses revealed a statistically significant association between heat exposure and CHD occurrence in cohort studies (pooled OR: 1.141; 95% CI: 1.005-1.296), whereas no significant association was found in case-control studies (pooled OR: 1.039; 95% CI: 0.934-1.156). Similarly, analysis based on exposure context showed a significant association in the ambient heat exposure subgroup (pooled OR: 1.080; 95% CI: 1.005-1.161), but not in the occasional exposure subgroup (pooled OR: 1.039; 95% CI: 0.634-1.700). CONCLUSION: This systematic review and meta-analysis provide evidence that maternal exposure to high ambient temperatures during pregnancy may be associated with an increased risk of CHD in offspring. These findings highlight the importance of integrating counseling on climate-related health risks into both prenatal care and public health policy.
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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 | 0.012 | 0.031 |
| Meta-epidemiology (narrow) | 0.003 | 0.001 |
| Meta-epidemiology (broad) | 0.018 | 0.041 |
| Bibliometrics | 0.007 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 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".