Table 1 Characteristics of participants by pre-pregnancy BMI
Variables | Total (n = 4890) | Pre-BMI underweight (n = 665) | Pre-BMI normal (n = 3474) | Pre-BMI overweight (n = 639) | Pre-BMI obesity (n = 112) | F/χ 2 | p |
|---|---|---|---|---|---|---|---|
Age, Mean ± SD | 30.59 ± 3.57 | 31.94 ± 3.88 | 32.65 ± 4.10 | 32.71 ± 4.23 | 30.59 ± 3.57 | 34.848 | < 0.001 |
Gestational weight gain, Mean ± SD | 39.21 ± 0.99 | 39.26 ± 1.02 | 39.19 ± 0.98 | 38.89 ± 0.88 | 39.21 ± 0.99 | 5.282 | 0.001 |
Gestational weight gain, n (%) |  |  |  |  |  | 382.345 | < 0.001 |
 Insufficient | 999 (20.4) | 194 (29.2) | 741 (21.3) | 58 (9.1) | 6 (5.4) |  |  |
 Adequate | 2059 (42.1) | 356 (53.5) | 1507 (43.4) | 172 (26.9) | 24 (21.4) |  |  |
 Excessive | 1832 (37.5) | 115 (17.3) | 1226 (35.3) | 409 (64) | 82 (73.2) |  |  |
Method of conception, n (%) |  |  |  |  |  | 30.376 | < 0.001 |
 Assisted reproductive technology | 859 (17.6) | 72 (10.8) | 627 (18) | 141 (22.1) | 19 (17) |  |  |
 Conceived Naturally | 4031 (82.4) | 593 (89.2) | 2847 (82) | 498 (77.9) | 93 (83) |  |  |
Place of residence, n (%) | Â | Â | Â | Â | Â | - | 0.405 |
 Rural | 218 (4.5) | 38 (5.7) | 148 (4.3) | 27 (4.2) | 5 (4.5) |  |  |
 Urban | 4672 (95.5) | 627 (94.3) | 3326 (95.7) | 612 (95.8) | 107 (95.5) |  |  |
Annual household income (10,000 RMB (1410 USD)/year), n (%) |  |  |  |  |  | 44.903 | < 0.001 |
 ~10 | 1542 (31.5) | 205 (30.8) | 1028 (29.6) | 259 (40.5) | 50 (44.6) |  |  |
 20 ~ 30 | 1491 (30.5) | 191 (28.7) | 1082 (31.1) | 190 (29.7) | 28 (25) |  |  |
 30~ | 1857 (38) | 269 (40.5) | 1364 (39.3) | 190 (29.7) | 34 (30.4) |  |  |
Occupation, n (%) | Â | Â | Â | Â | Â | 1.963 | 0.580 |
 Employed | 4376 (89.5) | 591 (88.9) | 3122 (89.9) | 564 (88.3) | 99 (88.4) |  |  |
 Unemployed | 514 (10.5) | 74 (11.1) | 352 (10.1) | 75 (11.7) | 13 (11.6) |  |  |
Education, n (%) |  |  |  |  |  | 35.197 | < 0.001 |
 ~College/vocational | 1187 (24.3) | 138 (20.8) | 821 (23.6) | 189 (29.6) | 39 (34.8) |  |  |
 Undergraduate | 2566 (52.5) | 382 (57.4) | 1793 (51.6) | 334 (52.3) | 57 (50.9) |  |  |
 Postgraduate~ | 1137 (23.3) | 145 (21.8) | 860 (24.8) | 116 (18.2) | 16 (14.3) |  |  |
Parity, n (%) |  |  |  |  |  | 19.191 | < 0.001 |
 Nulliparous | 3976 (81.3) | 581 (87.4) | 2799 (80.6) | 507 (79.3) | 89 (79.5) |  |  |
 Multiparous | 914 (18.7) | 84 (12.6) | 675 (19.4) | 132 (20.7) | 23 (20.5) |  |  |
Ethnic, n (%) | Â | Â | Â | Â | Â | - | 0.858 |
 Han | 4797 (98.1) | 655 (98.5) | 3404 (98) | 628 (98.3) | 110 (98.2) |  |  |
 non-Han | 93 (1.9) | 10 (1.5) | 70 (2) | 11 (1.7) | 2 (1.8) |  |  |
a Smoking status, n (%) | Â | Â | Â | Â | Â | - | 0.110 |
 No | 4772 (97.7) | 642 (96.5) | 3400 (98) | 622 (97.5) | 108 (97.3) |  |  |
 Yes | 111 (2.3) | 23 (3.5) | 69 (2) | 16 (2.5) | 3 (2.7) |  |  |
b Drinking status, n (%) | Â | Â | Â | Â | Â | 3.927 | 0.270 |
 No | 2999 (61.4) | 390 (58.6) | 2141 (61.7) | 404 (63.3) | 64 (57.7) |  |  |
 Yes | 1884 (38.6) | 275 (41.4) | 1328 (38.3) | 234 (36.7) | 47 (42.3) |  |  |