Prenatal diagnosis of sickle cell anemia in twin pregnancies and identification by VNTRs

Abstract

Background: Sickle cell anemia (SCA) is an inherited disorder of hemoglobin synthesis that is characterized by life-long severe hemolytic anemia, attacks of pain crisis, and chronic organ system damage. In this study, prenatal diagnosis was performed to three couples (families A, B, and C) with twin pregnancies who were at risk for SCA.

Methods: The SCA carrier state of the couples were confirmed at molecular level. Chorionic villus samples (CVS) of twins were obtained at 10-12 weeks of gestation. Amplification refractory mutation system (ARMS) and restriction fragment length polymorphism (RFLP) techniques were applied to determine and confirm the presence of the sickle cell anemia of the fetuses. Identification of each twin, confirmation of parentage and elimination of maternal contamination of chorionic villus samples were ruled out by variable number of tandem repeats (VNTR) analysis of four different loci [D1S80 (pMCT118), ApoB, IgJH, D4S95].

Results: We found that one of the fetuses was heterozygous for SCA and the other was normal in family A; in family B both fetuses were heterozygous and in family C both fetuses were normal.

Conclusion: Prenatal diagnosis is the major way of prevention of the genetic disorders including sickle cell anemia. Prenatal diagnosis of twins contains additional risks such as confusion in differentiation leading to false molecular diagnosis. VNTR loci analysis is a useful tool and can be safely used for the elimination of all problems mentioned above.