The differences in the frequencies of HLA-DRB1-associated haplotypes in elderly and young Bulgarians are presented on Table 1, where DRB1*11- (A*01~DRB1*11, HF young: 0.0451, HF elderly: 0.1048, OR = 2.48, p = 0.030) and DRB1*16- (A*02~B*35~DRB1*16 HF young: 0, HF elderly: 0.0323, OR = 18.26, p = 0.005) associated haplotypes were found to prevail significantly among elderly Bulgarians (Table 1). Here, HLA-DRB1 is linked to hydrops fetalis.