Ala16Val SOD2 polymorphism is associated with higher pregnancy rates in in vitro fertilization cycles

Abstract

Objective: To investigate whether the Ala16Val polymorphism in the SOD2 gene, encoding for mitochondrial manganese superoxide dismutase (SOD), is associated with [1] infertility and [2] the pregnancy rate (PR) in IVF cycles.

Design: Prospective case-control study.

Setting: Public university and public university hospital.

Patient(s): A total of 362 newborns (nonselected population) and 148 infertile women undergoing an IVF cycle, from which 44 became pregnant and 104 did not.

Intervention(s): Blood samples extracted from the patients and newborn umbilical cord.

Main outcome measure(s): Genotype and allele distribution of the Ala16Val polymorphism in the SOD2 gene using the tetra-primer amplification refractory mutation system-polymerase chain reaction (PCR).

Result(s): The polymorphism distribution of the subfertile women was similar to that of a nonselected population. The SOD2 Ala allele frequency was 49% both in controls and IVF patients. In IVF population the Ala/Ala SOD2 genotype was 25%, with a 28% Val/Val homozygous. In contrast, the Ala/Ala genotype was associated with higher PRs in IVF (47% in Ala/Ala vs. 23% in no Ala/Ala). A multivariate logistic regression analysis revealed that the Ala/Ala genotype was an independent predictor of pregnancy (odds ratio [OR] = 3.29), followed by the number of transferred embryos (OR = 2.37) and age (OR = 0.84).

Conclusion(s): The Ala/Ala SOD2 genotype is a significant independent predictor of the occurrence of pregnancy in IVF. Data also support a role for antioxidant defense, particularly in the mitochondria, in conception in IVF.