ASSOCIATION BETWEEN MATERNAL HETEROZYGOSI TY FOR 5 BLOOD-GROUPS AND REPRODUCTIVE SUCCESS

Background: In man, blood groups are polymorphic genetic systems. Mate rnal fetal incompatibility phenomena should lead to an elimination rat her than a maintenance of these polymorphisms. A possible mechanism th at could explain the persistence of these polymorphisms in natural pop ulations is a selective reproductive advantage of heterozygous individ uals. Aim: To explore the relationship between maternal heterozygosity for five blood groups and some obstetrical variables related to gesta tional success. Material and methods: Using a case control design, to every mother giving birth to a malformed child a consecutive mother, w hose offspring was normal, was assigned as control. All women were typ ified for ABO, Rh, Kidd, MNSs and Duffy blood groups. Results: Two hun dred two women were studied. There was only one stillbirth, born from a heterozygous mother for all analyzed loci. Mothers that were heteroz ygous or homozygous for all loci had a higher frequency of malformed c hildren. Women homozygous for all loci had a higher frequency of livin g offspring than the rest of the sample. Conclusions: Heterozygous mot hers for these genetic systems have a reproductive disadvantage.