Table 4

Prepregnancy sociodemographic characteristics of 536 098 pregnant women

VariablesN (%)Prepregnancy BMI (kg/m2)*p Value
All536 09821.06±2.67
Age, years<0.0001†
 21–24134 575 (25.10)20.78±2.53
 25–29265 633 (49.55)20.88±2.59
 30–34100 674 (18.78)21.54±2.83
 35–4935 216 (6.57)22.10±2.92
Ethnicity<0.0001‡
 Han507 235 (94.62)21.06±2.67
 Other28 863 (5.38)21.14±2.71
Occupation<0.0001†
 Farmer409 344 (76.36)21.18±2.72
 Factory worker52 242 (9.74)20.72±2.42
 Other74 512 (13.90)20.62±2.49
Educational level<0.0001†
 None1125 (0.21)21.46±2.89
 Primary school23 741 (4.43)21.42±2.96
 Junior middle school351 529 (65.57)21.23±2.70
 Senior middle school104 955 (19.58)20.72±2.52
 University and more54 748 (10.21)20.47±2.44
Smoking<0.0001‡
 No534 278 (99.66)21.06±2.67
 Yes1820 (0.34)21.36±3.05
Drinking<0.0001†
 No519 894 (96.98)21.06±2.67
 Casual16 030 (2.99)20.90±2.72
 Often174 (0.03)21.59±3.50
Previous pregnancy<0.0001‡
 No351 440 (65.56)20.80±2.48
 Yes184 658 (34.44)21.55±2.94
Previous PTB<0.0001‡
 No535 067 (99.81)21.06±2.67
 Yes1031 (0.19)21.71±3.23
Previous SB<0.0001‡
 No531 855 (99.21)21.05±2.66
 Yes4243 (0.79)22.11±3.33
Previous SM<0.0001‡
 No521 864 (97.34)21.04±2.65
 Yes14 234 (2.66)21.05±3.16
Previous birth defects<0.0001‡
 No534 348 (99.67)21.06±2.67
 Yes1750 (0.33)22.12±3.18
  • *Data are given as mean±SD.

  • †One-way analysis of variance.

  • ‡Student's t-test.

  • BMI, body mass index; PTB, preterm birth; SB, stillbirth; SM, spontaneous miscarriage.