[Successful preimplantation genetic diagnosis for beta-thalassemia using primer extension preamplification].

Objective: To achieve preimplantation genetic diagnosis (PGD) of the couples at risk of having children with beta-thalassemia, as an alternative to prenatal diagnosis.

Methods: Two couples carrying different thalassemia mutations of codon 41/42 and codon intervening sequence 2 position 654 received standard in vitro fertilization treatment and intracytoplasmic sperm injection, embryo biopsy and the whole genome was amplified by primer extension preamplification (PEP). Nested polymerase chain reaction was then used to amplify two mutation sites separately. Both were detected by reverse dot-blot.

Results: A total of 35 oocytes were retrieved from the two patients. Among them, 87% showed two pronuclei, and embryo biopsy was performed on 16 of these embryos and 25 blastomeres were obtained. The amplification efficacy was 84%. The genotype study of non-transferred and surplus embryos showed 15% of allele drop-out rate. Five embryos were transferred to the uterus of both patients. One pregnancy achieved, resulted in live healthy twin births, which confirmed the results of PGD.

Conclusions: This unaffected pregnancy resulting from PGD by PEP for beta-thalassemia demonstrates that this technique can be a effective diagnostic tool for carrier couples who desire a healthy child.