Table 5. Interaction between maternal passive smoking during pregnancy and joint genotype of CYP1A1 BsrD I and GSTs on risk of spontaneous PTD.
| Passive smoking | Genotype | Case (n = 198) | Control (n = 524) | ORa(95%CI) | P-value | |
| CYP1A1 BsrD I | GSTs | N. (%) | N. (%) | |||
| No | AA | Present | 38 (19.2%) | 149 (28.4%) | 1 | |
| No | AA | Null | 12 (6.1%) | 54 (10.3%) | 0.94 (0.45–1.95) | 0.863 |
| No | AG/GG | Present | 35 (17.7%) | 118 (22.5%) | 1.14 (0.67–1.95) | 0.636 |
| No | AG/GG | Null | 16 (8.1%) | 48 (9.2%) | 1.19 (0.59–2.42) | 0.613 |
| Yes | AA | Present | 30 (15.2%) | 61 (11.6%) | 1.80 (1.01–3.22) | 0.050 |
| Yes | AA | Null | 15 (7.6%) | 26 (5.0%) | 2.33 (1.11–4.89) | 0.030 |
| Yes | AG/GG | Present | 34 (17.2%) | 58 (11.1%) | 2.17 (1.23–3.83) | 0.008 |
| Yes | AG/GG | Null | 18 (9.1%) | 10 (1.9%) | 7.01 (2.91–16.86) | 0.000 |
| Interaction | 3.00 (1.17–7.74) | 0.023 | ||||
a.
ORa adjusted for family income, maternal age, education level, prepregnancy BMI and CYP1A1 Msp 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 BsrD I + GSTs with eight levels was set as dummy independent variable, and the first level as reference category.