The vertical axis is the percentage of early-onset persistent wheezers divided by the sum of early-onset persistent wheezers and non-wheezers (n = 791). For each genotype strata, reference was ETS-0. *, p value < 0.05; **, p value < 0.001. ETS-0, mothers did not smoke during pregnancy and children were not exposed to household ETS; ETS-1, mothers did not smoke during pregnancy, but children were exposed to household ETS; ETS-2, mothers smoked during pregnancy and children were exposed to household ETS. SNP, single nucleotide polymorphism; rs1800925, rs2066960, rs1295686, rs20541 and rs1295686 are five SNPs within the interleukin13 gene. SNPs rs1295686, rs20541, and rs1295686 were in a block. Therefore haplotype analysis was based on SNPs rs1800925, rs2066960, and rs20541. # The most common haplotype pair, CCG/CCG, constructed based on SNPs rs1800925, rs2066960, and rs20541, using PHASE 2.0.2 software [34].