Covariates Preterm(n=285) Preterm(n=285) Full-term(n=6216) Full-term(n=6216) PTB rates(%) Χ2 P-value
n % n %
Mother
Age (years) 11.229 0.004
<25 17 5.96 520 8.37 3.17
25-30 106 37.19 2785 44.80 3.67
>30 162 56.84 2911 46.83 5.27
Occupation 5.200 0.023
Other 210 73.68 4940 79.47 4.08
Housewife 75 26.32 1276 20.53 5.55
Education (years) 3.719 0.156
≤9 27 9.47 568 9.14 4.54
10-12 61 21.40 1064 17.12 5.42
>12 197 69.12 4584 73.75 4.12
Pregnancy
Parity 4.554 0.033
Primiparous 122 42.81 3074 49.45 3.82
Multiparous 163 57.19 3142 50.55 4.93
Delivery mode 24.499 <0.001
natural birth 114 40.00 3426 55.12 3.22
cesarean 171 60.00 2790 44.88 5.78
Complications 80.40 <0.001
Yes 46 16.14 268 4.31 14.65
No 239 83.86 5948 95.69 3.86
Work <0.001 0.997
Yes 175 61.40 3829 61.60 4.45
No 110 38.60 2387 38.40 4.41
Tobacco exposure 0.0688 0.793
Yes 41 14.39 941 15.14 4.18
No 244 85.61 5275 84.86 4.42
Infant
Gender 1.639 0.200
Male 164 57.54 3209 51.62 4.86
Female 121 42.46 3007 48.38 3.87
Family
Income(yuan/month) 5.415 0.020
<6000 49 17.19 767 12.34 6.00
≥6000 236 82.81 5449 87.66 4.15