Human Reproduction, Vol. 17, No. 1, 25-31,
January 2002
© 2002 European Society of Human Reproduction and Embryology
Pregnancies following blastocyst stage transfer in PGD cycles at risk for ß-thalassaemic haemoglobinopathies
1 Embryogenesis Fertility Clinic, Kifissias Avenue, Athens 15125 and 2 Medical Genetics, Athens University, St. Sophia's Children's Hospital, Athens 11527, Greece
BACKGROUND: Preimplantation genetic diagnosis (PGD) usually involves blastomere biopsy 3 days post-insemination (p.i.), followed by genetic analysis and transfer of unaffected embryos later on day 3 or 4. We evaluate a strategy involving embryo biopsy on day 3 p.i., genetic analysis on day 4 and, following culture in blastocyst sequential media, transfer of unaffected embryos on day 5 p.i. METHODS: PGD cycles were initiated in 15 couples at risk of transmitting ß-thalassaemia major. Oocyte retrieval and ICSI were performed according to standard protocols. Embryo culture used blastocyst sequential media. Embryos were biopsied on day 3 p.i. using acid Tyrode's for zona drilling, and the single blastomeres were genotyped by a protocol involving nested polymerase chain reaction and denaturing gradient gel electrophoresis analysis. RESULTS: Forty of 109 (37%) embryos biopsied on day 3 p.i. developed to blastocysts by day 5 p.i., with at least one blastocyst available for transfer in 12 cycles (80%). Genotype analysis characterized 51/109 (47%) embryos unaffected for ß-thalassaemia major, of which 28 were blastocysts. Transfer of 37 day 5 p.i. embryos (blastocysts and non blastocysts) initiated eight clinical pregnancies. Implantation rate per embryo transferred was 12/37 (32%). CONCLUSIONS: Embryo biopsy on day 3, followed by delayed transfer until day 5 p.i. offers a novel and effective strategy to overcome the time limit encountered when performing PGD, without compromising embryo implantation.
Key words: ß-thalassaemia/blastocyst stage transfer/Ca2+Mg2+ free medium/preimplantation genetic diagnosis
3 To whom correspondence should be addressed at: Centre for Reproductive Medicine, Alpha Lab, Anastasiou 8, Athens 115 24, Greece. E-mail: gpalme{at}otenet.gr
By the time of publication all embryos of the three ongoing pregnancies had been confirmed as unaffected by prenatal diagnosis. The triplet pregnancy was selectively reduced to twins at the request of the parents and all three ongoing pregnancies went to term, resulting in the birth of five more healthy babies.
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