Apolipoprotein E (Apo E) gene polymorphisms and recurrent pregnancy loss: a meta-analysis

BACKGROUND: Recently, a relationship between recurrent pregnancy loss (RPL) and Apolipoprotein E (Apo E) gene polymorphisms has been proposed. In order to investigate the real association between Apo E polymorphisms and RPL, our meta-analysis was carried out. METHODS: We estimated the association with RPL risk under dominant and recessive models, in combination with the OR and RR with a 95% confidence interval (CI), which was used to assess the association between RPL and Apo E polymorphisms. RESULTS: According to our criterion, there were 6 studies included. The dominant model used the E4/E3 group and the OR was 1.919 (95 %CI: 1.016-3.625, I(2) = 53.8%), the RR was 1.308 (95%Cl: 1.071-1.598) suggesting that carriers of the E4 allele would have a higher risk of causing spontaneous miscarriages. In addition, the OR was 0.727 (95%CI: 0.566-0.932, I(2) = 0.0%) and RR was 0.923 (95%CI: 0.867-0.982) in a fixed model for E3/E3 homozygotes versus other genotypes, suggesting that the Apo E3 polymorphism could be a protective factor. The OR was 1.365 (95% CI: 1.029-1.811, I(2) = 0 .0%) in a fixed model comparing the E2 allele with the E3 allele, suggesting that Apo E2 polymorphisms may contribute to RPL as a risk factor. Furthermore, after conducting sensitivity analysis in the E4/E3 group, the results showed this to be consistent and the OR was 2.249 (95%CI: 1.474-3.431). CONCLUSIONS: There is a close association between RPL and Apo E gene polymorphisms. For RPL, the Apo E4 polymorphism could be a risk factor, the Apo E3 polymorphism may be a protective factor and the Apo E2 polymorphism may be another potential risk factor.