Table 1.
Basic characteristics of preterm low birth weight cases and controls [n (%)].
| Characteristics | Cases (n = 102) | Controls (n = 306) |
|---|---|---|
| Maternal age | ||
| <25 | 19 (18.6) | 57 (18.6) |
| 25-29 | 39 (38.2) | 117 (38.2) |
| ≥30 | 44 (43.1) | 132 (43.1) |
| Education | ||
| More than high school | 38 (37.3) | 178 (58.1) |
| High school | 18 (17.7) | 66 (21.66) |
| Less than high school | 46 (45.1) | 60 (19.6) |
| Missing | 0 (0.0) | 2 (0.7) |
| Occupational status | ||
| Employed | 74 (72.6) | 252 (82.3) |
| Un-employed | 28 (27.5) | 47 (15.4) |
| Missing | 0 (0) | 7 (2.3) |
| Household income | ||
| ≥50,000 yuan per year | 28 (27.5) | 146 (47.7) |
| <50,000 yuan per year | 66 (64.7) | 138 (45.1) |
| Missing | 8 (7.8) | 22 (7.2) |
| Body mass index | ||
| Normal (18.5-23.9) | 58 (56.9) | 195 (63.7) |
| Underweight (<18.5) | 26 (25.5) | 68 (22.2) |
| Overweight (≥24) | 13 (12.8) | 38 (12.4) |
| Missing | 5 (4.9) | 5 (1.6) |
| Smoking during pregnancy | ||
| No | 98 (96.1) | 304 (99.4) |
| Yes | 1 (10) | 0 (0.0) |
| Missing | 3 (2.9) | 2 (0.7) |
| Passive smoking during pregnancy | ||
| No | 74 (72.5) | 239 (78.1) |
| Yes | 28 (27.5) | 59 (19.3) |
| Missing | 0 (0) | 8 (2.6) |
| Alcohol use during pregnancy | ||
| No | 98 (96.1) | 300 (98.0) |
| Yes | 1 (1.0) | 1 (0.3) |
| Missing | 3 (2.9) | 5 (1.6) |
| Parity | ||
| 1 | 76 (74.5) | 248 (81.1) |
| ≥2 | 26 (25.5) | 58 (18.9) |
| Cesarean delivery | ||
| No | 11 (10.8) | 37 (12.1) |
| Yes | 91 (89.2) | 269 (87.9) |
| Hypertension | ||
| No | 88 (86.3) | 297 (97.1) |
| Yes | 14 (13.78) | 9 (2.9) |
| Diabetes | ||
| No | 100 (98.0) | 292 (95.4) |
| Yes | 2 (2.0) | 14 (4.6) |
| Heart disease | ||
| No | 102 (100.0) | 306 (100.0) |
| Yes | 0 (0.0) | 0 (0.0) |
| Multivitamin supplements during pregnancy | ||
| Yes | 45 (44.1) | 124 (40.5) |
| No | 56 (54.9) | 179 (58.5) |
| Missing | 1 (1.0) | 3 (1.0) |