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Referrals and indications for PGD in .NET Encoder Code128 in .NET Referrals and indications for PGD

Referrals and indications for PGD use none none generating tointegrate none with none Microsoft .NET Micro Framework Excluding aneupl none none oidy screening, the number of referrals for chromosomal abnormalities has increased tremendously and in the last few years over 1000 cycles were started for structural chromosome abnormalities (Sermon et al., 2007). Couples in whom one of the partners carries a chromosomal abnormality, such as a balanced Robertsonian or reciprocal translocation, may be at high risk of repeated miscarriage and/ or viable offspring with an unbalanced chromosome pattern, leading to multiple congenital anomalies and mental retardation in the child.

Also, future parents with a structural chromosome abnormality, such as an interstitial deletion of chromosome 22q11.2, leading to the clinical signs and symptoms of velo-cardio-facial (VCF) syndrome, may opt for PGD (Iwarsson et al., 1998).

The risk of an abnormal chromosome pattern in offspring depends on the exact nature of the chromosomal abnormality as well as on the family history. It is of great importance to determine this risk in advance (Stephenson & Sierra, 2006). Infertile males are also at increased risk of carrying a translocation or other structural chromosome abnormality and previously would not have been able to reproduce (Simopoulou et al.

, 2003). With the use of ICSI they are now able to father children. However, such pregnancies are still at risk for being chromosomally abnormal, and it is appropriate to combine ICSI treatment with PGD in such cases.

Currently, in most centers cleavage-stage embryos are analyzed with two or more fluorescence in situ hybridization (FISH) probes. In this way it may be determined if an embryo is unbalanced or not, but it is not possible to make a distinction between balanced carrier embryos and chromosomally normal embryos, and this should be explained to the couple. In PGD for chromosomal abnormalities the number of unbalanced embryos is often remarkably high (70 80 percent), leading to a low pregnancy rate per cycle (Simopoulou et al.

, 2003; Ogilvie & Scriven, 2004; Stephenson & Sierra, 2006). Pregnancy rate per transfer is better, as once a normal embryo is diagnosed, the major issue has been solved. To offer PGD to female carriers of balanced translocations, Munn and colleagues (Munn et al.

, 2000) analyzed the first polar body of their eggs. If biopsied within a couple of hours after oocyte retrieval, first polar bodies are still in metaphase and may be assessed. Chromosome abnormalities 8: Clinical aspects of preimplantation genetic diagnosis Table 8.1 Referr als for preimplantation genetic diagnosis (PGD): comparison of data collections I and V. Data collection none none I (1997 to September 1998). Data collection V (January to December 2002). Chromosomal 83 1 none for none 150 Structural chromosome abnormality 40 208 Aneuploidy screening 27 882 Other reasons for numerical screening 16 60 Monogenic disorders 233 453 Autosomal dominant 47 111 Autosomal recessive 88 102 X-linked (sexing) 95 109 Others or unknown mode of inheritance 3 131 ESHRE PGD Consortium (1999); Harper et al. (2006), with permission from Oxford University Press..

by chromosome pa inting. A major drawback of this method is that only maternal translocations can be analyzed (Sermon et al., 2004).

A point of concern regarding PGD for chromosomal abnormalities is that for an individual couple the benefit of PGD, in terms of ongoing pregnancy rate of a healthy child, compared to a spontaneous conception, eventually followed by prenatal diagnosis has not yet been proven (Sugiura-Ogasawara & Suzumori, 2005; Stephenson & Sierra, 2006). This would require a randomized study of spontaneous pregnancy followed by prenatal testing versus PGD, which is ethically full of concerns. Sugiura-Ogasawara and colleagues (Sugiura-Ogasawara et al.

, 2004; Sugiura-Ogasawara & Suzumori, 2005) calculated a cumulative rate for a successful pregnancy of 68 percent for PGD and of 68.1 percent for a natural pregnancy. However, for translocation carriers who have experienced repeated miscarriages, or unbalanced offspring, PGD may be the only way to achieve a normal pregnancy .

. The first PGD di none for none agnosis for a monogenic disorder was for cystic fibrosis in 1992 (Handyside et al., 1992). The number of referrals and the number of treatments for monogenic disorders has shown a gradual increase over the years (Table 8.

1) (Sermon et al., 2007). Nowadays, PGD is feasible for the most frequent autosomal heritable disorders (Renwick & Ogilvie, 2007).

PGD for autosomal dominant disorders is applied on a routine basis for several trinucleotide repeat disorders such as Huntington disease, myotonic dystrophy,.
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