Experience in preimplantation genetic diagnosis for exclusion of homozygous a thalassemia

• Published in: Prenatal diagnosis 2006-01, Vol.26 (11), p.1029-1036
• Main Authors: Chan, Vivian, Ng, Ernest HY, Yam, Irene, Yeung, William SB, Ho, P C, Chan, T K
• Format: Article
• Language: English
• ISSN: 0197-3851
• DOI: 10.1002/pd.1550

Objective: To report our experience in preimplantation genetic diagnosis (PGD) for the exclusion of homozygous a thalassemia. Patients and Methods: PGD was performed on nine couples with a 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 a 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 a 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 a thalassemia is possible by single cell PCR. The transfer and successful implantation of unaffected embryos ensure birth of disease-free babies.