The impact of genetics profile (gene polymorphisms) in obese non-PCOS women entering an IVF/ICSI program

Data concerning the effects of increased body mass index (BMI) on ovarian and pregnancy outcome are rich, but the results are rather controversial. Regarding pharmacogenetics, gene polymorphisms of hormonal receptor genes, such as Estrogen Receptor alpha (ESR1), Estrogen Receptor beta (ESR2) and FSH receptor (FSHR) genes, are associated with ovarian stimulation and pregnancy outcome and may constitute a useful tool for ART experts for the prediction of this outcome. The aim of this study is to track differences in the distribution of gene polymorphisms among obese non-PCOS and non-obese patients concerning three distinct genes which are involved in the ovarian stimulation mechanism: PvuII polymorphism of ESR1 gene, RsaI polymorphism of ESR2 gene and Ser680Asn variation of FSHR gene, using restriction fragment length polymorphism analysis and real-time polymerase chain reaction. A total of 151 normally ovulating female patients underwent IVF or ICSI. Interestingly, the pregnancy rate in the BMI≥30 kg/m² group was higher in a statistically significant way (40.9% versus 17.8%, p=0.023). The obese patients of this study were in need of increased total FSH dose in order to achieve a satisfactory oocyte number (p<0.001) and needed more days of stimulation (p=0.002), but also presented lower basal FSH levels (p=0.032), which may explain, to an extend, the better pregnancy outcome. Concerning the polymorphisms of ESR1, ESR2 and FSHR genes, we did not observe differences in the genotype distribution when we compared the obese non-PCOS population with the non-obese population. Thus, obesity does not constitute an additional indication to perform a genetic analysis before entering an IVF/ICSI program.