Genes are passed on from one generation to another. The phenotype or trait of a gene depends on the genotype. Genotype can be described as a particular combination of the gene on the chromosomes. Depending upon the inheritance pattern of the genotype, a certain combination or variation of the gene can be harmful resulting in a disease phenotype. It can be traumatic to undergo an abortion if the baby is detected prenatally for some life threatening genetic disease. In families where there is a clinical history of such genetic diseases it very important that the disease causing combination is excluded in order to have a healthy baby. Preimplantation genetic diagnosis or PGD is such a platform where the disease causing gene combination is probed and embryos harbouring such combinations are excluded. Thus, even in families which manifest fatal genetic disorders, PGD gives a chance to have a healthy baby.
Over more than 100 genetic diseases can be investigated in an embryo for PGD.
Most of the risks involved in PGD treatment are similar to those for conventional IVF. For more information, see:With PGD, there is also the possibility that:
It is possible that, instead of removing and testing one or two cells from a 2-3 day old embryo, some centres may allow the embryo to develop to 5-6 days, when there are 100-150 cells.
At this stage, cells within an embryo have separated into two types: cells which will form the fetus (inner cell mass) and cells which will form the placenta (trophectoderm).
More cells can be removed at this stage (from the trophectoderm) without compromising the viability of the embryo, possibly leading to a more accurate test.
It is difficult to assess success rates for PGD because there is currently little data available. Most women use this treatment not because they have fertility problems but because they want to avoid having a child with a genetic disease.
As with most fertility treatments, success depends on many factors, including the woman’s age and whether a cause of infertility has been identified.Sometimes no embryos are suitable for transfer to the womb, for reasons including:
In 2010 (the year for which the most recent data is available) 311 women received 383 cycles of PGD. This resulted in 121 live births (live birth rate of 31.6% per cycle started).