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Table 1 Demographic characteristics of female participants by paternal smoking

From: Paternal smoking and preterm birth: a population-based retrospective cohort study among non-smoking women aged 20–49 years in rural China

Characteristics Without paternal smoking
(N = 3,760,013)
Paternal smoking
(N = 1,538,030)
P-value
Maternal age at LMP, years     < 0.001
 20–24 1,854,321 (49.32) 787,071 (51.17)  
 25–29 1,435,650 (38.18) 552,020 (35.89)  
 20–34 370,544 (9.85) 155,818 (10.13)  
 34–39 84,127 (2.24) 36,769 (2.39)  
 ≥ 40 15,371 (0.41) 6352 (0.41)  
Paternal age at LMP, years    0.698
 20–24 1,187,331 (31.58) 513,454 (33.38)  
 25–29 1,723,283 (45.83) 663,335 (43.13)  
 20–34 608,613 (16.19) 251,416 (16.35)  
 34–39 175,640 (4.67) 80,289 (5.22)  
 ≥ 40 51,510 (1.37) 23,516 (1.53)  
NA 13,636 (0.36) 6020 (0.39)  
Higher education, N (%) 478,692 (12.73) 169,000 (10.99)  < 0.001
Han Chinese ethnic, N (%) 3,466,467 (92.19) 1,396,953 (90.83)  < 0.001
BMI   ef 0.015
 Underweight 505,479 (13.44) 249,029 (16.19)  
 Normal weight 2,750,542,(73.15) 1,058,090 (68.80)  
 Over weight 401,370 (10.67) 184,711 (12.01)  
 Obese 81,635 (2.17) 42,358 (2.75)  
 NA 20,987 (0.56) 3842 (0.25)  
Alcohol drinking, ml/day     < 0.001
 No 3,682,327 (97.93) 1,479,682 (96.21)  
 1–10 7943 (0.21) 7113 (0.46)  
 11–50 6172 (0.16) 5652 (0.37)  
 ≥ 51 2535 (0.07) 2531 (0.16)  
 NA 61,036 (1.62) 43,052 (2.80)  
Primipara, No. (%) 2,655,253 (70.62) 1,010,155 (65.68)  < 0.001
History of adverse pregnancy outcome, N (%) 93,903 (2.50) 67,638 (4.40)  < 0.001
Maternal passive smoking, min/day     < 0.001
 No 3,677,977 (97.82) 1,377,704 (89.58)  
 1–15 52,305 (1.39) 97,893 (6.36)  
 ≥ 16 23,515 (0.63) 59,690 (3.88)  
 NA 6216 (0.17) 2743 (0.18)  
Paternal passive smoking, min/day     < 0.001
 No 3,619,027 (96.25) 1,173,620 (76.31)  
 1–15 80,040 (2.13) 165,487 (10.76)  
 ≥ 16 52,868 (1.41) 192,236 (12.50)  
 NA 8078 (0.21) 6687 (0.43)  
  1. BMI body mass index, LMP last menstrual period, TSH thyroid stimulating hormone