Maternal demographic characteristic of AGA group and SGA group matched according to 1:4 PSM analysis
| Variables | Items | AGA group（n=1528） | SGA group（n=382） | x2 | P value |
| Maternal age | 18~35 | 1220 (79.8) | 305 (79.8) | 0.395 | 1.000b |
| 36~45 | 305 (20) | 76 (19.9) | |||
| ≥46 | 3 (0.2) | 1 (0.3) | |||
| Nationality | The Han | 1498 (98) | 372 (97.4) | 0.638 | 0.424 |
| Minority nationality | 30 (2) | 10 (2.6) | |||
| Residence | Urban | 825 (54) | 196 (51.3) | 0.884 | 0.347 |
| Rural | 703 (46) | 186 (48.7) | |||
| Education | Elementary and below | 528 (34.6) | 126 (33) | 3.476 | 0.324 |
| Secondary/high school | 223 (14.6) | 45 (11.8) | |||
| College/university | 770 (50.4) | 210 (55) | |||
| Postgraduate or above | 7 (0.5) | 1 (0.3) | |||
| Occupation | Manual worker | 284 (18.6) | 69 (18.1) | 2.074 | 0.557 |
| Mental worker | 708 (46.3) | 192 (50.3) | |||
| Unemployed | 381 (24.9) | 86 (22.5) | |||
| Freelance | 155 (10.1) | 35 (9.2) | |||
| Marital status | Unmarried | 27 (1.8) | 8 (2.1) | 0.685 | 0.730b |
| Married | 1497 (98) | 374 (97.9) | |||
| Divorced or widowed | 4 (0.3) | 0 (0) | |||
| Height (cm) | ≥155 | 1248 (81.7) | 275 (72) | 22.232 | <0.001 |
| 150–154.9 | 197 (12.9) | 73 (19.1) | |||
| 145–149.9 | 79 (5.2) | 29 (7.6) | |||
| <145 | 4 (0.3) | 5 (1.3) | |||
| Pre-pregnancy BMI (kg/m2) | Normal | 1130 (74) | 271 (70.9) | 9.175 | 0.01 |
| Underweight | 172 (11.3) | 64 (16.8) | |||
| Overweight/obese | 226 (14.8) | 47 (12.3) | |||
| GWG rate | Inadequate gain | 690 (45.2) | 199 (52.1) | 6.107 | 0.047 |
| Appropriate gain | 539 (35.3) | 121 (31.7) | |||
| Excessive gain | 299 (19.6) | 62 (16.2) |
Bold values were statistically significant. b Fisher exact test.
AGA, appropriate for gestational age; BMI, body mass index; GWG, gestational weight gain; PSM, propensity score matching; SGA, small for gestational age.