GSTM1 and childhood onset asthma: Prenatal TSE significantly increased the risk of childhood asthma in females with the GSTM1 null genotype (30.0% versus 9.4%, P = 0.001, OR: 4.107, 95% CI: 1.699–10.107) compared with the effect in the other 3 groups (Table 3 and Figure 1).