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Table 1 Comparison of maternal, paternal, newborn characteristics and adverse birth outcomes between nulliparity and multiparity

From: Parity and the risks of adverse birth outcomes: a retrospective study among Chinese

  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)  
  1. 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
  2. Abbreviations: PTB Preterm Birth, LBW Low Birth Weight, SGA Small for Gestational Age, SD Standard Deviation