Live birth following preimplantation genetic screening for trisomy 21. Should aneuploidy screening be offered to all older patients undergoing IVF?

A 42-year-old female patient with history of secondary infertility was referred to our assisted conception unit for in vitro fertilization (IVF). Before her referral, she had two cycles of IVF at another centre; the first was unsuccessful and, after conceiving at the second attempt, the pregnancy was terminated at 14 weeks' gestation following a positive nuchal translucency scan and a diagnosis of trisomy 21 (Down syndrome) by a chorionic villous biopsy performed in the first trimester. The screening tests for trisomy 21 were offered to the patient in view of her advanced age. Subsequent karyotyping revealed that both partners had a normal chromosomal complement. Following genetic counselling, the couple were offered IVF treatment along with preimplantation genetic screening for trisomy 21. Four of the five embryos were suitable for biopsy, and one blastomere from each embryo was analyzed using fluorescent in situ hybridization for chromosome 21. The analysis revealed that two embryos had trisomy 21, one had monosomy 21, and only one embryo was diploid for chromosome 21. The single diploid embryo was transferred to the uterus on day 3, and resulted in an uneventful pregnancy and delivery of a healthy live-born male.

Live birth following the first mutation specific pre-implantation genetic diagnosis for haemophilia A.

Haemophilia A is an X-linked, recessive, inherited bleeding disorder which affects 1 in 5000 males born worldwide. It is caused by mutations in the FactorVIII (F8) gene on chromosome Xq28. We describe for the first time two mutation specific, single cell protocols for pre-implantation genetic diagnosis (PGD) of haemophilia. A that enable the selection of both male and female unaffected embryos. This approach offers an alternative to sexing, frequently used for X-linked disorders, that results in the discarding of all male embryos including the 50% that would have been normal. Two families with a history of severe haemophilia. A requested carrier diagnosis and subsequently proceeded to PGD. The mutation in family 1 is a single nucleotide substitution c.5953C > T, R1966X in exon 18 and in family 2, c.5122C > T, R1689C in exon 14 of the F8 gene. Amplification efficiency was compared between distilled water and SDS/proteinase K cell lysis (98.0%, 96/98 and 80%, 112/140 respectively) using 238 single lymphocytes. Blastomeres from spare IVF cleavage-stage embryos donated for research showed amplification efficiencies of 83.3% (45/54) for the R1966X and 92.9% (13/14) for the R1689C mutations. The rate of allele dropout (ADO) on heterozygous lymphocytes was 1.1% (1/93) for R1966X and 5.94% (6/101) for R1689C mutations. A single PGD treatment cycle for family 1 resulted in two embryos for transfer but these failed to implant. However, with family 2, two embryos were transferred to the uterus on day 4 resulting in a successful singleton pregnancy and subsequent live birth of a normal non-carrier female.