Table 4. Interaction between maternal passive smoking during pregnancy and joint genotype of CYP1A1 Msp I and GSTs on risk of spontaneous PTD.
| Passive smoking | Genotype | Case (n = 198) | Control (n = 524) | ORa(95%CI) | P-value | |
| CYP1A1 Msp I | GSTs | N. (%) | N. (%) | |||
| No | TT | Present | 30 (15.2%) | 110 (21.0%) | 1 | |
| No | TT | Null | 11 (5.6%) | 41 (7.8%) | 1.04 (0.47–2.29) | 0.918 |
| No | TC/CC | Present | 43 (21.7%) | 157 (30.0%) | 0.98 (0.57–1.67) | 0.947 |
| No | TC/CC | Null | 17 (8.6%) | 61 (11.6%) | 0.95 (0.47–1.93) | 0.902 |
| Yes | TT | Present | 25 (12.6%) | 45 (8.6%) | 1.82 (0.95–3.48) | 0.072 |
| Yes | TT | Null | 7 (3.5%) | 16 (3.1%) | 1.64 (0.61–4.41) | 0.326 |
| Yes | TC/CC | Present | 39 (19.7%) | 74 (14.1%) | 1.85 (1.04–3.26) | 0.035 |
| Yes | TC/CC | Null | 26 (13.1%) | 20 (3.8%) | 4.72 (2.28–9.77) | 0.000 |
| Interaction | 2.66 (1.19–5.97) | 0.017 | ||||
a.
ORa adjusted for family income, maternal age, education level, prepregnancy BMI and CYP1A1 BsrD I genotype.
b.
GSTs “null” if both GSTM1 and GSTT1 “null”, GSTs “present” if either GSTM1 or GSTT1 “present”.
c.
% for distribution within the case and control groups respectively.
d
.The variable of passive smoking+CYP1A1 Msp I+ GSTs with eight levels was set as dummy independent variable, and the first level as reference category.