Table 1.
Meta-analyses results for LBW or term low birth weight (TLBW) (*) and PM2.5 exposure during the entire pregnancy.
| Descriptive Information on Meta-Study and All Input Studies | Meta-Risk Estimates for Specific Analyses | ||||||
|---|---|---|---|---|---|---|---|
| Reference | Country/Region | Range of Participants/Births | Exposure Range (Using Study Metrics) | Adjusted for/Subgroup | Studies Included in Risk Estimate Analysis (n) | OR/RR (95% CI), PM2.5 per 10 µg/m3 Increment | Heterogeneity (I2) |
| Sapkota et al. 2012 (*) [28] | USA (n = 9), Canada and Taiwan (n = 2 each), Germany, Brazil, Korea and (n = 1 each) | Participants: 128 to 374,167; Cases: 69 to 21,450 |
Range of PM2.5 means (where reported): 5.1–11.9 µg/m3; Range of PM2.5 medians (where reported): 13.5–14.4 µg/m3 |
NA | 4 | 1.09 [0.90, 1.32] | 57.4% |
| Stieb et al. 2012 [30] | North America (n = 27), Europe (n = 18), Asia (n = 10), Australia (n = 4), South America (n = 3) | Births: 153 to 3,303,834 | PM2.5 Min./Max. average 24 h concentrations (µg/m3) among all studies: Min. 1.8 Max. 44.2 |
NA | 6 | 1.05 [0.99, 1.12] | 85.5% |
| Dadvand et al. 2013 (*) [27] | North America (6), Europe (5), South America (1), Asia (1), Oceania (1) | Births: ~1000 to ~2 m | Range of PM2.5 medians (where reported): 3.98–20.3 µg/m3 | NA | 7 | 1.17 [1.08, 1.26] | 92.3% |
| Adjusted for maternal SES | 1.10 [1.03, 1.18] | 89.7% | |||||
| Adjusted for maternal SES and centre specific covariates ** | 1.04 [0.99, 1.09] | 68.5% | |||||
| Zhu et al. 2015 [31] | USA (n = 17), Canada (n = 2), Australia (n = 2), Netherlands, UK, Poland and Norway (n = 1 each) | Study population: 481 to 1,5480,904 | NA | NA | 6 | 1.05 [1.02, 1.07] | 39.70% |
| Sun et al. 2016 [7] | USA (n = 23), Multi-country (n = 2), Canada, Spain, Netherlands, UK, Poland, Norway, Australia (n = 1 each) | Participants: 481 to 3,545,177 | Range of PM2.5 (where reported): 5.1–43.8 µg/m3; Except (Fleischer et al., 2014 [35]): 1.4–98.1 µg/m3 |
19 | 1.09 [1.03, 1.15] | 92.6% | |
| USA | 14 | 1.08 [1.02, 1.14] | 94.3% | ||||
| Other setting | 5 | 1.14 [1.04, 1.25] | 36.1% | ||||
| Li et al. 2017 (*) [24] | USA n = 17, Canada n = 2, Europe n = 3, other n =1 | Births: 3853 to 3,545,177 | Range of PM2.5 means (where reported) 1.82–22.11 µg/m3 | NA | 4 | 1.05 [0.98, 1.12] | 85.0% |
| Guo et al. 2019 [33] | USA (n = 17), Canada (n = 4), Brazil and China (n = 3 each), Spain, Australia, South Korea, and multi-country (n = 2 each), Iran, UK, Taiwan, Norway, Sweden, and Japan (n = 1 each) | Births: 225 to 2,402,545 | NA | NA | 6 | 1.00 [0.98, 1.03] | 73.3% |
| Ji et al. 2019 [34] | USA and Canada (n = 3 each), Iran, Korea, Netherlands, Taiwan, Brazil, UK, Spain, multi-country (n = 1 each) | Births: 225 to 423,719 | NA | NA | 6 | 1.04 [0.99, 1.09] | 67.4% |
| Li et al. 2020 *** [32] | USA (n = 20), China (n = 9), Korea (n = 5), Canada (n = 4), Japan, Lithuania, Spain, UK (n = 2 each), Australia, Czech republic, India, Iran, Peru, Poland, Puerto Rico, multi-country (n = 1 each) | 225 to 3,545,177 | NA | 29 | 1.08 [1.04, 1.12] | 86.0% | |
| The Americas | 18 | 1.07 [1.02, 1.12] | >50% | ||||
| Asia | 7 | 1.04 [0.99,1.10] | >50% | ||||
| Europe | 4 | 1.38 [1.19, 1.59] | <50% | ||||
* term low birth weight. ** centre-specific covariates = covariates specific to the locations where the data were generated/collected. *** the authors report relative risk (RR) estimates.