Table 4

 Preterm birth prevalence, odds ratios (95%CI) by social class, and RII by maternal factors and time, Scotland 1980–2000

Social class1980–19841985–19891990–19941995–2000
%OR95%CI%OR95%CI%OR95%CI%OR95%CI
*p for interaction term.
I3.413.913.913.711
II4.01.20(1.10, 1.31)4.21.09(1.00, 1.19)4.41.12(1.03, 1.21)4.51.21(1.11, 1.32)
IIInm4.91.48(1.36, 1.61)5.11.34(1.23, 1.46)5.41.40(1.29, 1.53)5.41.47(1.35, 1.60)
IIIm4.81.42(1.31, 1.54)5.01.30(1.20, 1.41)5.11.32(1.22, 1.44)5.41.46(1.34, 1.58)
IV5.71.71(1.57, 1.85)5.51.45(1.33, 1.57)5.41.40(1.29, 1.52)5.91.60(1.47, 1.74)
V5.81.75(1.60, 1.91)5.51.45(1.32, 1.59)5.51.43(1.30, 1.56)5.71.56(1.41, 1.73)
Undetermined14.44.78(4.37, 5.23)7.11.91(1.74, 2.09)6.51.70(1.56, 1.85)6.91.90(1.75, 2.07)
Total5.25.05.25.4
RII p*p*p*p*
Overall 2.45(2.31, 2.59)1.60(1.51, 1.70)1.52(1.44, 1.61)1.75(1.65, 1.86)
Marital status <0.0010.0010.0040.18
Married2.31(2.16, 2.46)1.48(1.38, 1.59)1.43(1.32, 1.54)1.65(1.51, 1.79)
Single1.76(1.51, 2.06)1.14(1.00, 1.29)1.11(0.99, 1.26)1.45(1.30, 1.62)
Other1.45(1.12, 1.88)1.20(0.97, 1.49)1.27(1.05, 1.53)1.50(1.30, 1.73)
Maternal age <0.0010.0020.0010.005
<201.48(1.26, 1.74)1.12(0.95, 1.33)1.03(0.84, 1.25)1.39(1.12, 1.73)
20–342.35(2.20, 2.52)1.55(1.45, 1.66)1.50(1.41, 1.61)1.66(1.55, 1.78)
⩾353.08(2.50, 3.80)1.69(1.37, 2.08)1.69(1.40, 2.03)2.12(1.81, 2.48)
Maternal height 0.540.390.27<0.001
<155 cm2.15(1.89, 2.44)1.38(1.20, 1.58)1.32(1.13, 1.53)1.54(1.31, 1.80)
155 cm–164 cm2.36(2.19, 2.56)1.55(1.43, 1.68)1.43(1.32, 1.55)1.69(1.56, 1.84)
>164 cm2.33(2.07, 2.62)1.51(1.35, 1.69)1.55(1.40, 1.72)1.71(1.55, 1.87)
Parity 0.01<0.001<0.001<0.001
02.07(1.91, 2.25)1.24(1.14, 1.35)1.25(1.15, 1.36)1.31(1.20, 1.42)
1–22.48(2.27, 2.72)1.81(1.65, 1.99)1.69(1.54, 1.85)2.04(1.86, 2.23)
3+2.44(2.00, 2.98)1.63(1.32, 2.00)1.38(1.12, 1.70)2.17(1.77, 2.66)