Pre-implantation genetic diagnosis.

The aim of pre-implantation genetic diagnosis (PGD) is to characterize the genetic status of the cells (usually single cells) that have been biopsied from oocytes/zygotes or embryos created in vitro during assisted reproductive treatment. PGD is a multi-step procedure that requires close collaboration between gynaecologists who are experts in assisted reproduction, embryologists who are experts in micromanipulation of germ cells and in embryo biopsy and geneticists who are experts in genetic analysis at the single-cell level. PGD can be applied as a form of early pre-natal diagnosis with the aim to establish a pregnancy unaffected by a haemoglobinopathy. In addition, PGD can identify embryos that are human leukocyte antigen compatible with an existing sibling affected by a haemoglobinopathy to support a haematopoietic stem cell transplantation. PGD has an advantage over conventional pre-natal diagnosis as it precludes the need to consider terminating an affected ongoing pregnancy. However, PGD is a multi-step, complex and costly procedure with an unpredictable outcome and thus is most suited for couples with an unsuccessful reproductive history or challenging reproductive status. In addition, PGD supports the cure of an affected child. Couples who decide to undergo a PGD cycle should be fully aware of the advantages and limitations. The three teams of health practitioners involved (gynaecologists, embryologists and geneticists) should thoroughly counsel the couples and provide support at all the stages: the initial evaluation of their genetic and reproductive status, all steps of assisted reproduction, embryo biopsy, genetic analysis and, when relevant, follow-up of pregnancy and baby(ies) delivered.