Outcome characteristics
| Total | A | B | C | D | Ungraded | P value | |
| (N=3160) | (N=32) | (N=463) | (N=930) | (N=1444) | (N=291) | ||
| Birth weight (g) | |||||||
| Mean (SD) | 3197.6 (614.5) | 3364.6 (700.1) | 3218.7 (621.1) | 3259.2 (569.6) | 3157.8 (621.7) | 3146.4 (676.3) | 0.001 |
| Birth weight z-score | |||||||
| Mean (SD) | −0.1 (1.0) | 0.2 (1.3) | −0.1 (1.0) | −0.0 (1.1) | −0.2 (1.0) | −0.2 (1.0) | 0.002 |
| Preterm birth | |||||||
| No | >2823 (>89.34%) | >26 (>81.25%) | 416 (89.85%) | 844 (90.75%) | 1281 (88.71%) | 256 (87.97%) | 0.353 |
| Yes | >327 (>10.35%) | <5 (<15.63%) | 47 (10.15%) | 86 (9.25%) | 163 (11.29%) | 35 (12.03%) | |
| Low birth weight | |||||||
| No | >3076 (>97.34%) | >26 (>81.25%) | 449 (96.98%) | 919 (98.82%) | 1405 (97.30%) | 277 (95.19%) | 0.114 |
| Yes | >74 (>2.34%) | <5 (<15.63%) | 14 (3.02%) | 11 (1.18%) | 39 (2.70%) | 14 (4.81%) | |
| Average PM2.5 µg/m3 exposure during pregnancy | |||||||
| Mean (SD) | 7.0 (1.2) | 7.2 (0.9) | 6.8 (1.1) | 6.7 (1.2) | 7.2 (1.1) | 7.4 (1.1) | <0.001 |
PM, particulate matter.