Characteristic
Total
PTB
PTB
LBW
LBW
SGA
SGA
No (n=5188)
Yes (n=224)
No (n=5059)
Yes (n=126)
No (n=4395)
Yes (n=316)
Agec 26.6±3.7 26.6±3.7 27.0±3.6 26.6±3.7 26.0±3.5 26.5±3.7 25.8±3.5
<25 2523 (31.2) 1623 (31.3) 65 (29.0) 1574 (31.1) 44 (34.9) 1377 (31.3) 123 (38.9)
25~29 1688 (46.6) 2420 (46.6) 103 (46.0) 2355 (46.6) 61 (48.4) 2068 (47.1) 145 (45.9)
≥30 1201 (22.2) 1145 (22.1) 56 (25.0) 1130 (22.3) 21 (16.7) 950 (21.6) 48 (15.2)
Residencea
Rural 1143 (21.1) 4104 (79.1) 165 (73.7) 3985 (78.8) 101 (80.2) 3457 (78.7) 256 (81.0)
Education
Senior high school or lower 3075 (56.8) 2954 (56.9) 121 (54.0) 2877 (56.9) 72 (57.1) 2502 (56.9) 179 (56.6)
Employment
Unemployed 3114 (57.5) 2985 (57.5) 129 (57.6) 2911 (57.5) 69 (54.8) 2533 (57.6) 166 (52.5)
Average family income (RMB per year)c
≤49,999 2285 (42.2) 2180 (42.0) 105 (46.9) 2130 (42.1) 60 (47.6) 1857 (42.3) 155 (49.1)
Pre-pregnancy BMI (kg/m2)c
Underweight 973 (18.0) 925 (17.8) 48 (21.4) 924 (18. 3) 33 (26.2) 824 (18.7) 89 (28.2)
Normal 3680 (68.0) 3541 (68. 3) 139 (62.1) 3457 (68.3) 76 (60.3) 2997 (68.2) 197 (62.3)
Overweight 599 (11.1) 567 (10.9) 32 (14.3) 533 (10.5) 15 (11.9) 451 (10.3) 26 (8.2)
Obese 160 (3.0) 155 (3.0) 5 (2.2) 145 (2.9) 2 (1.6) 123 (2.8) 4 (1.3)
GWGc
Appropriate 499 (9.2) 474 (9.1) 25 (11.2) 436 (8.6) 10 (7.9) 369 (8.4) 14 (4.4)
Insufficient 4816 (89.0) 4625 (89.1) 191 (85.3) 4542 (89.8) 114 (90.5) 3958 (90.1) 299 (94.6)
Excessive 97 (1.8) 89 (1.7) 8 (3.6) 81 (1.6) 2 (1.6) 68 (1.5) 3 (0.9)
Smoking
Never 5049 (93.3) 4842 (93.3) 207 (92.4) 4720 (93.3) 121 (96.0) 4097 (93.2) 293 (92.7)
Former 267 (4.9) 252 (4.9) 15 (6.7) 248 (4.9) 4 (3.2) 218 (5.0) 18 (5.7)
Current 96 (1.8) 94 (1.8) 2 (0.9) 91 (1.8) 1 (0.8) 80 (1.8) 5 (1.6)
Drinking
Never 4294 (79.3) 4120 (79.4) 174 (77.7) 4017 (79.4) 104 (82.5) 3486 (79.3) 252 (79.7)
Former /Current 1118 (20.7) 1068 (20.6) 50 (22.3) 1042 (20.6) 22 (17.5) 909 (20.7) 64 (20.3)
Paritybc
≥1 2344 (43.3) 2258 (43.5) 85 (37.9) 2203 (43.5) 40 (31.7) 1888 (43.0) 85 (26.9)
HDPab
Yes 101 (1.9) 91 (1.8) 10 (4.5) 88 (1.7) 6 (4.8) 79 (1.8) 7 (2.2)
Pre-eclampsia
Yes 40 (0.7) 37 (0.7) 3 (1.3) 37 (0.7) 2 (1.6) 30 (0.7) 3 (0.9)
GDMc
Yes 369 (6.8) 347 (6.7) 22 (9.8) 340 (6.7) 7 (5.6) 292 (6.6) 7 (2.2)
Physical activity during pregnancy
Low 1804 (33.3) 1733 (33.4) 71 (31.7) 1687 (33.3) 43 (34.1) 1470 (33.4) 118 (37.3)
Medium 1805 (33.4) 1721 (33.2) 84 (37.5) 1679 (33.2) 47 (37.3) 1455 (33.1) 101 (32.0)
High 1803 (33.3) 1734 (33.4) 69 (30.8) 1693 (33.5) 36 (28.6) 147 (33.4) 97 (30.7)