β2-adrenergic receptor gene polymorphisms and pregnancy outcome

Aims: The association between alleles at two loci of the polymorphic β2-adrenergic receptor (β2AR) gene and pregnancy outcome was determined. Methods: In a case-control study, buccal swabs obtained from 159 mother-infant pairs after a preterm or term birth were analyzed by gene amplification and endonuclease digestion for polymorphisms at codons 16 and 27 of the β2AR gene. Results: Homozygosity for allele A at codon 16 (Arg-16) occurred in 26 (20.5%) of 127 mothers with a term birth and in none of the mothers who had a spontaneous preterm birth (p = 0.002). Conversely, 24 of 32 (75.0%) mothers with a spontaneous preterm birth, as compared to 58 of 127 (45.7%) mothers with term births, were Arg-16/allele G (Gly-16) heterozygotes (p = 0.003). There was no relation between pregnancy outcome and infant genotype at codon 16 or maternal or infant genotypes at codon 27. The alleles at codon 16 and 27 were in linkage disequilibrium and the combinations of Arg-16-Gln-27 homozygosity (p = 0.04) and Arg-16/Gly-16-Gln homozygous (p = 0.01) were associated with a decreased and increased rate of spontaneous preterm birth, respectively. Conclusion: At codon 16 of the β2-AR gene, maternal Arg-16 homozygosity protects against, and Gly-16 predisposes to spontaneous preterm birth.