Table 3.
Characteristics of women and twin infants.
| N (%) | |
|---|---|
| Age at delivery | |
| < = 19 | 38 (0.55) |
| 20–24 | 812 (11.73) |
| 25–29 | 2719 (39.26) |
| 30–34 | 2479 (35.80) |
| ≥35 | 877 (12.66) |
| Education level | |
| Less than 9 years | 1525 (22.08) |
| 9–12 years | 1659 (24.02) |
| More than 12 years | 3723 (53.90) |
| Parity | |
| Nullipara | 5259 (75.94) |
| Multipara | 1666 (24.06) |
| Gravidity | |
| <3 | 5465 (78.92) |
| ≥3 | 1460 (21.08) |
| Pre-pregnancy BMI (kg/m 2 ) | |
| Underweight(<18.5) | 854 (12.33) |
| Normal (18.5–23.9) | 5225 (75.45) |
| Overweight (24–27.9) | 715 (10.32) |
| Obese (≥28) | 131 (1.89) |
| Total GWG | Chinese-recommended/IOM- recommended |
| Low | 1629 (23.52) 2000 (32.94) |
| Normal | 3694 (53.34) 2714 (44.70) |
| High | 1602 (23.13) 1357 (22.35) |
| Birth type | |
| Caesarean section | 6507 (93.96) |
| Vaginal delivery | 418 (6.04) |
| Offspring sex | |
| Male/male pairs | 2427 (35.05) |
| Female/female pairs | 2235 (32.27) |
| Male/female pairs | 2263 (32.68) |
| Apgar score 1 minute | |
| ≥7 | 13313 (96.12) |
| <7 | 537 (3.88) |
| Apgar score 5 minute | |
| ≥7 | 13712 (99.00) |
| <7 | 138 (1.00) |
| Gestational weeks | |
| <28 | 7 (0.10) |
| 28–32 | 373 (5.39) |
| 33–36 | 3230 (46.64) |
| ≥37 | 3315 (47.87) |