Summary effect estimates for the relation between ambient air pollution exposure and the risk of stillbirth
| Heterogeneity | ||||||
|---|---|---|---|---|---|---|
| Air pollutant | Studies contributing to the summary effect estimate | Fixed effects Summary effect estimates EE (95% CI) | Random effects Summary effect estimates EE (95% CI) | χ2 | p Value | I2 (%) |
| SO2 (3 ppb) | Faiz 2012, Green 2015, Hwang 2011 | 1.019 (0.989 to 1.049) | 1.022 (0.984 to 1.062) | 2.49 | 0.288 | 19.6 |
| 1st trimester | Faiz 2012, Green 2015, Hwang 2011, | 0.997 (0.975 to 1.020) | 1.040 (0.962 to 1.125) | 10.34 | 0.006 | 80.7 |
| 2nd trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.003 (0.977 to 1.030) | 1.003 (0.977 to 1.030) | 1.79 | 0.408 | 0.0 |
| 3rd trimester | Faiz 2012, Green 2015, Hwang 2011 | 0.996 (0.967 to 1.026) | 1.042 (0.951 to 1.142) | 11.26 | 0.004 | 82.2 |
| NO2 (10 ppb) | Faiz 2012, Green 2015, Hwang 2011 | 1.049 (1.012 to 1.088) | 1.066 (0.965 to 1.178) | 9.78 | 0.008 | 79.6 |
| 1st trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.025 (0.996 to 1.054) | 1.035 (0.983 to 1.089) | 4.43 | 0.109 | 54.8 |
| 2nd trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.005 (0.977 to 1.034) | 1.007 (0.948 to 1.071) | 5.83 | 0.054 | 65.7 |
| 3rd trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.015 (0.980 to 1.051) | 1.015 (0.980 to 1.051) | 1.88 | 0.391 | 0.0 |
| CO (0.4 ppm) | Faiz 2012, Green 2015, Hwang 2011 | 1.022 (0.995 to 1.050) | 1.025 (0.985 to 1.066) | 2.52 | 0.284 | 20.5 |
| 1st trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.002 (0.983 to 1.022) | 1.011 (0.967 to 1.057) | 2.92 | 0.232 | 31.6 |
| 2nd trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.002 (0.979 to 1.025) | 1.015 (0.948 to 1.087) | 5.60 | 0.061 | 64.3 |
| 3rd trimester | Faiz 2012, Green 2015, Hwang 2011 | 1.014 (0.992 to 1.038) | 1.052 (0.973 to 1.138) | 10.19 | 0.006 | 80.4 |
| PM10 (10 µg/m3) | Hwang 2011, Kim 2007 | 1.012 (0.986 to 1.039) | 1.014 (0.948 to 1.085) | 6.67 | 0.010 | 85.0 |
| 1st trimester | Hwang 2011, Kim 2007 | 1.015 (0.991 to 1.039) | 0.998 (0.936 to 1.064) | 2.18 | 0.140 | 54.1 |
| 2nd trimester | Hwang 2011, Kim 2007 | 0.968 (0.944 to 0.993) | 1.005 (0.905 to 1.116) | 5.31 | 0.021 | 81.2 |
| 3rd trimester | Hwang 2011, Kim 2007 | 0.995 (0.968 to 1.022) | 1.021 (0.919 to 1.134) | 10.96 | 0.001 | 90.9 |
| PM2.5 (4 µg/m3) | Faiz 2012, Green 2015 | 1.021 (0.996 to 1.046) | 1.021 (0.996 to 1.046) | 0.18 | 0.669 | 0.0 |
| 1st trimester | Faiz 2012, Green 2015 | 1.002 (0.982 to 1.022) | 1.042 (0.920 to 1.180) | 2.35 | 0.126 | 57.4 |
| 2nd trimester | Faiz 2012, Green 2015 | 1.011 (0.996 to 1.026) | 1.040 (0.940 to 1.152) | 1.92 | 0.166 | 47.9 |
| 3rd trimester | Faiz 2012, Green 2015 | 1.00 (0.981 to 1.020) | 1.00 (0.981 to 1.020) | 0.23 | 0.631 | 0.0 |
| O3 (10 ppb) | Green 2015, Hwang 2011 | 1.005 (0.982 to 1.029) | 1.002 (0.971 to 1.034) | 1.24 | 0.265 | 19.6 |
| 1st trimester | Green 2015, Hwang 2011 | 1.001 (0.983 to 1.020) | 1.001 (0.983 to 1.020) | 0.13 | 0.714 | 0.0 |
| 2nd trimester | Green 2015, Hwang 2011 | 1.004 (0.985 to 1.022) | 0.991 (0.944 to 1.040) | 3.18 | 0.074 | 68.6 |
| 3rd trimester | Green 2015, Hwang 2011 | 1.025 (1.006 to 1.043) | 1.012 (0.966 to 1.060) | 2.72 | 0.099 | 63.2 |