title: Experience in preimplantation genetic diagnosis for exclusion of homozygous alpha degrees thalassemia.
abstract: OBJECTIVE
  To report our experience in preimplantation genetic diagnosis (PGD) for the exclusion of homozygous alpha degrees thalassemia.
  
  
  METHODS
  PGD was performed on nine couples with alpha degrees 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 alpha degrees 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 alpha degrees 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 alpha degrees thalassemia is possible by single cell PCR. The transfer and successful implantation of unaffected embryos ensure birth of disease-free babies.
authors.affiliation: University Department of Medicine, Queen Mary Hospital, Hong Kong. vnchana@hkucc.hku.hk
authors.forename: Vivian
authors.initials: V
authors.lastname: Chan
authors.forename: Ernest H Y
authors.initials: EH
authors.lastname: Ng
authors.forename: Irene
authors.initials: I
authors.lastname: Yam
authors.forename: William S B
authors.initials: WS
authors.lastname: Yeung
authors.forename: P C
authors.initials: PC
authors.lastname: Ho
authors.forename: T K
authors.initials: TK
authors.lastname: Chan
mesh_terms: D000483:Alleles; D001757:Blastomeres; D005260:Female; D006720:Homozygote; D006801:Humans; D009154:Mutation; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011256:Pregnancy Outcome; D019836:Preimplantation Diagnosis / Q000379:methods*; D027724:Reproductive Techniques, Assisted; D017085:alpha-Thalassemia / Q000175:diagnosis* / Q000196:embryology / Q000235:genetics