title: Blastocyst biopsy versus cleavage stage biopsy and blastocyst transfer for preimplantation genetic diagnosis of beta-thalassaemia: a pilot study.
abstract: BACKGROUND
  Trophectoderm biopsy at the blastocyst stage is an emerging approach in preimplantation genetic diagnosis (PGD). This study aimed to compare genotyping success and implantation rates in PGD cycles for beta-thalassaemia following biopsy at the cleavage versus the blastocyst stage, with transfer of blastocysts.
  
  
  METHODS
  This pilot study included 20 cycles: Group A: 10 cycles, day 3 blastomere biopsy, day 5 transfer; Group B: 10 cycles, day 5 trophectoderm biopsy, day 6 transfer. Standard-assisted reproduction and laser biopsy procedures were used. Biopsied cells were genotyped using real-time PCR multiplexed with fluorescent microsatellite analysis.
  
  
  RESULTS
  In Group A, 131 fertilized eggs developed to 101 embryos suitable for single blastomere biopsy; 76/101 blastomeres were diagnosed (75.2%), 30 unaffected blastocysts were transferred resulting in six pregnancies (eight fetal hearts, 26.7% implantation rate). In Group B, 128 fertilized eggs developed to 53 blastocysts for trophectoderm biopsy (four to five cells), with 50/53 blastocysts diagnosed (94.3%), 21 unaffected blastocysts transferred and 6 pregnancies initiated (10 fetal hearts, 47.6% implantation rate). Overall, nine pregnancies reached >10 weeks gestation and were confirmed unaffected by prenatal diagnosis, with 12 healthy babies born.
  
  
  CONCLUSIONS
  This pilot study suggests that trophectoderm biopsy and blastocyst transfer may be more advantageous than cleavage stage biopsy with respect to outcome of PGD for monogenic diseases.
authors.affiliation: Centre for Human Reproduction, Genesis Hospital, Athens, Greece. georgiakokkali@mail.com
authors.forename: G
authors.initials: G
authors.lastname: Kokkali
authors.forename: J
authors.initials: J
authors.lastname: Traeger-Synodinos
authors.forename: C
authors.initials: C
authors.lastname: Vrettou
authors.forename: D
authors.initials: D
authors.lastname: Stavrou
authors.forename: G M
authors.initials: GM
authors.lastname: Jones
authors.forename: D S
authors.initials: DS
authors.lastname: Cram
authors.forename: E
authors.initials: E
authors.lastname: Makrakis
authors.forename: A O
authors.initials: AO
authors.lastname: Trounson
authors.forename: E
authors.initials: E
authors.lastname: Kanavakis
authors.forename: K
authors.initials: K
authors.lastname: Pantos
mesh_terms: D000328:Adult; D001706:Biopsy / Q000379:methods*; D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D004624:Embryo Transfer; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods; D006801:Humans; D008297:Male; D010865:Pilot Projects; D011247:Pregnancy; D019836:Preimplantation Diagnosis / Q000379:methods*; D017086:beta-Thalassemia / Q000175:diagnosis*