Experience in preimplantation genetic diagnosis for exclusion of homozygous α° thalassemia

Objective To report our experience in preimplantation genetic diagnosis (PGD) for the exclusion of homozygous α° thalassemia. Patients and Methods PGD was performed on nine couples with α° thalassemia genotype undergoing assisted reproduction. Oocytes were aspirated after ovarian stimulation and fertilized by intracytoplasmic sperm injection. One or two blastomeres were biopsied from the six- to eight-cell embryo. Single cell multiplex PCR of the normal and α° thalassemia alleles was performed for first round, followed by semi-nested PCR of the respective alleles using 5′-end labelled fluorescent primers. Only those embryos with a blastomere diagnosed as having at least one normal allele were selected for transfer. Results One hundred and twenty-six blastomeres from 82 embryos were analyzed. The rates of allele dropout was 10.2% and PCR failure 12.7%. Fifty-eight embryos (70.7%) had at least one normal allele, of which 31 were transferred to 13 prepared cycles and one triplet pregnancy achieved. The triplets showed no ultrasound features of homozygous α° thalassemia at 18 weeks and were delivered in healthy condition by caesarean section at 34 weeks. Their genotypes were confirmed by cord blood analysis. Conclusions PGD for α° thalassemia is possible by single cell PCR. The transfer and successful implantation of unaffected embryos ensure birth of disease-free babies. Copyright © 2006 John Wiley & Sons, Ltd.