Table 1.
Comparison of maternal, paternal, newborn characteristics and adverse birth outcomes between nulliparity and multiparity
| Total | Nulliparity | Multiparity | P | |
|---|---|---|---|---|
| N (%) | 746,410 | 427,986 (57.34) | 318,424 (42.66) | |
| Maternal characteristics | ||||
| Age (mean ± SD) | 28.32 ± 4.61 | 26.46 ± 3.77 | 30.86 ± 4.43 | < 0.001 |
| Race, n (%) | 0.772 | |||
| Han ethnicity | 719,994 (97.27) | 415,772 (97.28) | 304,222 (97.26) | |
| Other ethnicities | 20,204 (2.73) | 11,646 (2.72) | 8558 (2.74) | |
| Missing | 6212 | 568 | 5644 | |
| Residence, n (%) | < 0.001 | |||
| Urban | 243,868 (32.94) | 151,730 (35.49) | 92,138 (29.45) | |
| Rural | 496,488 (67.06) | 275,779 (64.51) | 220,709 (70.55) | |
| Missing | 6054 | 477 | 5577 | |
| Immigrant, n (%) | < 0.001 | |||
| Local residents | 458,356 (61.93) | 244,073 (57.11) | 214,283 (68.50) | |
| Immigrants | 281,811 (38.07) | 183,284 (42.89) | 98,527 (31.50) | |
| Missing | 190 | 152 | 38 | |
| Education, n (%) | < 0.001 | |||
| Primary school or below | 14,668 (9.58) | 3928 (0.92) | 10,740 (3.43) | |
| Junior high school | 133,422 (16.62) | 45,264 (10.59) | 88,158 (28.18) | |
| Senior high school | 324,707 (40.46) | 187,630 (43.89) | 137,077 (43.82) | |
| University or above | 267,559 (33.34) | 190,687 (44.60) | 76,872 (24.57) | |
| Missing | 6054 | 477 | 5577 | |
| Pre-pregnancy BMI (mean ± SD) | 21.59 ± 3.29 | 21.03 ± 3.12 | 22.35 ± 3.37 | < 0.001 |
| Pre-pregnancy obesity, n (%) | < 0.001 | |||
| No | 710,268 (95.95) | 415,926 (97.30) | 294,342 (94.11) | |
| Yes | 29,968 (4.05) | 11,530 (2.70) | 18,438 (5.89) | |
| Missing | 8071 | 1605 | 6466 | |
| Paternal characteristics | ||||
| Age (mean ± SD) | 29.87 ± 5.71 | 27.84 ± 4.94 | 32.64 ± 5.53 | < 0.001 |
| Race, n (%) | < 0.001 | |||
| Han ethnicity | 720,233 (97.64) | 415,145 (97.52) | 305,088 (97.80) | |
| Other ethnicities | 17,436 (2.36) | 10,563 (2.48) | 6873 (2.20) | |
| Missing | 8741 | 2278 | 6463 | |
| Newborn characteristics | ||||
| Sex, n (%) | 0.014 | |||
| Male | 386,918 (51.84) | 221,332 (51.71) | 165,586 (52.00) | |
| Female | 359,492 (48.16) | 206,654 (48.29) | 152,838 (48.00) | |
| Gestational week at delivery (mean ± SD) | 39.07 ± 1.34 | 39.23 ± 1.35 | 38.87 ± 1.30 | < 0.001 |
| Height, cm (mean ± SD) | 49.73 ± 1.50 | 49.71 ± 1.49 | 49.76 ± 1.50 | < 0.001 |
| Weight, kg (mean ± SD) | 3.28 ± 0.43 | 3.26 ± 0.43 | 3.31 ± 0.43 | < 0.001 |
| Adverse birth outcomes | ||||
| PTB, n (%) | < 0.001 | |||
| Yes | 34,827 (4.67) | 18,832 (4.40) | 15,995 (5.02) | |
| No | 711,583 (95.33) | 409,154 (95.60) | 302,429 (94.98) | |
| LBW, n (%) | < 0.001 | |||
| Yes | 22,740 (3.05) | 13,701 (3.20) | 9039 (2.84) | |
| No | 723,670 (96.95) | 414,285 (96.80) | 309,385 (97.16) | |
| SGA, n (%) | < 0.001 | |||
| Yes | 48,233 (6.46) | 32,295 (7.55) | 15,938 (5.01) | |
| No | 698,177 (93.54) | 395,691 (92.45) | 302,486 (94.99) | |
PTB was defined as gestational age < 37 weeks, LBW was defined as birth weight < 2500 g; SGA was defined as birth weight below 10th centile for specific gestational age and sex
Abbreviations: PTB Preterm Birth, LBW Low Birth Weight, SGA Small for Gestational Age, SD Standard Deviation