| No. (Weighted %) |  |  | ||
---|---|---|---|---|---|
Characteristic | Total | Exposure | Non-exposure | χ2 | P value |
Maternal age | |||||
 < 20 years | 1093 (2.39) | 93 (2.70) | 1000 (2.38) | 1.94 | 0.413 |
 20–34 years | 63,948 (86.41) | 2933 (86.70) | 61,015 (86.40) |  |  |
 > 34 years | 8364 (11.20) | 386 (10.60) | 7978 (11.22) |  |  |
Maternal education | |||||
 Low | 16,763 (36.38) | 911 (35.34) | 15,852 (36.41) | 9.83 | < 0.001 |
 Middle | 29,302 (39.70) | 1144 (44.18) | 28,158 (39.56) |  |  |
 High | 19,846 (23.93) | 529 (20.48) | 19,317 (24.03) |  |  |
Hukou | |||||
 Local | 62,833 (87.15) | 3303 (96.73) | 59,530 (86.81) | 230.02 | < 0.001 |
 Migrant | 10,150 (12.85) | 101 (3.27) | 10,049 (13.19) |  |  |
Pre-pregnant BMI | |||||
 Underweight | 6769 (12.95) | 266 (15.18) | 6503 (12.90) | 6.89 | 0.001 |
 Healthy weight | 39,463 (72.49) | 1208 (73.37) | 38,255 (72.47) |  |  |
 Overweight/Obese | 8105 (14.56) | 184 (11.45) | 7921 (14.64) |  |  |
History of preterm | |||||
 Yes | 899 (1.47) | 34 (1.04) | 865 (1.48) | 3.01 | 0.083 |
 No | 72,388 (98.53) | 3370 (98.96) | 69,018 (98.52) |  |  |
Artificial Conception | |||||
 Yes | 4690 (6.47) | 128 (3.33) | 4562 (6.58) | 50.10 | < 0.001 |
 No | 68,491 (93.53) | 3287 (96.67) | 65,204 (93.42) |  |  |
Parity | |||||
 Primiparous | 41,207 (47.37) | 1790 (52.69) | 39,417 (47.18) | 28.09 | < 0.001 |
 Multiparous | 32,062 (52.63) | 1613 (47.31) | 30,449 (52.82) |  |  |
Diabetes | |||||
 Yes | 770 (0.90) | 38 (0.98) | 732 (0.90) | 0.19 | 0.664 |
 No | 72,276 (99.10) | 3368 (99.02) | 68,908 (99.10) |  |  |
Heart disease | |||||
 Yes | 278 (0.32) | 21 (0.53) | 257 (0.32) | 2.78 | 0.095 |
 No | 72,998 (99.68) | 3393 (99.47) | 69,605 (99.68) |  |  |
Renal disease | |||||
 Yes | 121 (0.13) | 4 (0.10) | 117 (0.13) | 0.14 | 0.708 |
 No | 73,211 (99.87) | 3410 (99.90) | 69,801 (99.87) |  |  |
Autoimmune disease | |||||
 Yes | 206 (0.16) | 23 (0.69) | 183 (0.14) | 52.33 | < 0.001 |
 No | 72,764 (99.84) | 3391 (99.31) | 69,373 (99.86) |  |  |
Hyperthyroidism | |||||
 Yes | 270 (0.39) | 15 (0.44) | 255 (0.38) | 0.19 | 0.663 |
 No | 72,661 (99.61) | 3396 (99.56) | 69,265 (99.62) |  |  |
Hypothyroidism | |||||
 Yes | 991 (0.88) | 34 (1.13) | 957 (0.87) | 1.72 | 0.190 |
 No | 71,922 (99.12) | 3377 (98.87) | 68,545 (99.13) |  |  |
Asthma | |||||
 Yes | 57 (0.05) | 2 (0.06) | 55 (0.05) | 0.12 | 0.732 |
 No | 73,232 (99.95) | 3411 (99.94) | 69,821 (99.95) |  |  |
Gestational Diabetes | |||||
 Yes | 7372 (11.43) | 173 (5.99) | 7199 (11.63) | 64.48 | < 0.001 |
 No | 65,017 (88.57) | 3234 (94.01) | 61,783 (88.37) |  |  |
Gestational hypertension | |||||
 Yes | 3415 (4.16) | 149 (4.06) | 3266 (4.17) | 0.06 | 0.802 |
 No | 69,004 (95.84) | 3233 (95.94) | 65,771 (95.83) |  |  |
Gestational anemia | |||||
 Yes | 9293 (13.26) | 147 (4.90) | 9146 (13.55) | 167.22 | < 0.001 |
 No | 64,029 (86.74) | 3268 (95.10) | 60,761 (86.45) |  |  |
Gestational hyperthyroidism | |||||
 Yes | 300 (0.32) | 10 (0.27) | 290 (0.32) | 0.20 | 0.658 |
 No | 72,636 (99.68) | 3405 (99.73) | 69,231 (99.68) |  |  |
Gestational hypothyroidism | |||||
 Yes | 2024 (1.90) | 58 (2.16) | 1966 (1.90) | 0.73 | 0.394 |
 No | 70,910 (98.10) | 3357 (97.84) | 67,553 (98.10) |  |  |
Gestational asthma | |||||
 Yes | 45 (0.05) | 1 (0.02) | 44 (0.05) | 0.69 | 0.407 |
 No | 73,350 (99.95) | 3414 (99.98) | 69,936 (99.95) |  |  |
Multiple pregnancy | |||||
 Yes | 1569 (1.78) | 105 (2.72) | 1464 (1.75) | 10.76 | 0.001 |
 No | 71,921 (98.22) | 3311 (97.28) | 68,610 (98.25) |  |  |
Mode of delivery | |||||
 Cesarean | 27,096 (36.77) | 1838 (54.67) | 25,258 (36.14) | 332.93 | < 0.001 |
 Vaginal | 46,073 (63.23) | 1574 (45.33) | 44,499 (63.86) |  |  |
Infant sex | |||||
 Female | 34,170 (47.30) | 1636 (47.97) | 32,534 (47.27) | 0.45 | 0.504 |
 Male | 39,323 (52.70) | 1780 (52.03) | 37,543 (52.73) |  |  |