A modest but significant effect of CGB5 gene promoter polymorphisms in modulating the risk of recurrent miscarriage

OBJECTIVE: To confirm the effect of single nucleotide polymorphisms (SNPs) in chorionic gonadotropin beta (CGB) genes in modulating the susceptibility to recurrent miscarriage (RM) in Danes and in a meta-analysis across Danes and the discovery samples from Estonia and Finland.

DESIGN: Case-control association study, restriction fragment length polymorphism genotyping, resequencing.

SETTING: Fertility clinics at the Rigshospitalet, Copenhagen, and Aalborg Hospital, Aalborg, Denmark.

PATIENT(S): Four hundred fifty Danish women and men from couples with RM and 119 women with children and no miscarriages in new study. A total of 634 women and men from RM couples and 314 female controls in a combined study of Estonians, Finns, and Danes.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Distribution of CGB5 and CGB8 allele and haplotype frequencies in patients and controls.

RESULT(S): For the majority of studied SNPs, the allelic and haplotypic distribution differed statistically between the Danish and the previous Estonian-Finnish sample. In Danes, two CGB5 promoter SNPs (c5-155; c5-142) exhibited a nonsignificant trend for higher allele frequency in fertile women compared with RM patients. The meta-analysis of results from three populations confirmed a modest but significant effect on carriage of c5-155C (odds ratio = 0.64; 95% confidence interval [CI] 0.44-0.94) and c5-142A (odds ratio = 0.66; 95% CI, 0.45-0.94) variants in reducing the risk of RM. None of the investigated genetic variants in the CGB8 gene was associated with RM.

CONCLUSION(S): Carriage of particular variants in the promoter of the CGB5 gene seems to protect against RM. No common genetic variants in CGB5 and CGB8 were associated with increased RM susceptibility in the studied North European populations.