26. Embryo biopsy

only to improve the IVF rates. So the requirements of accuracy are less strict and high false positive results may be acceptable. The test should more importantly be less costly, rapid and

In preimplantation genetic diagnosis diagnostic accuracy is most important. The test should be highly sensitive and specific with very low false negative results. There are three procedures

The risks associated with ovarian stimulation should be empathically communicated. The couple should be given the option of not proceeding with IVF and PGD/PGS and the choice should be voluntary. The risks associated with embryo biopsy and extended cultures while waiting for the result of biopsy should be explained. The possibility that in case of a false positive result a healthy embryo will be discarded should be explained. The possibility that in case of a false negative result an abnormal embryo may be transferred should be explained. The couple should also be explained about the options of prenatal testing like maternal serum markers, fetal ultrasound, amniocentesis, chorionic villous sampling and fetal blood sampling. The couple should also be explained about the possibility that if all embryos are found affected embryo transfer will not be carried out. Finally the issue of embryos not transferred (discard,

The couple should also be made aware of alternative methods of avoiding genetic defects (like

Laser or mechanical dissection can be done for opening the zona pellucida and retrieval of the polar body [21, 22]. Laser assisted biopsy are less time consuming. Acid Tyrode solution used for chemical denudation of blastocysts is not tolerated by ovum and is not used for ovum

The removal of both polar bodies is done in the time window of 8–14 h. After fertilization. Simultaneous removal of both polar bodies is preferred over sequential removal of polar

Even with the biopsy of both polar bodies, around 26% of errors are missed. Even in the presence of an abnormal polar body screening 90% of embryos will still be euploid [23]. This is because copy number analysis only determines a relative loss or gain of genetic material-not an absolute copy number. Nondisjunction represents only 10% of errors; others are due to premature segregation of sister chromatins. When reciprocal errors occur for a given chromosome in first and second polar body, 90%of embryos will be euploid. So, with 55% of abnormal

polar body biopsy, blastomere biopsy and blastocyst biopsy [20] (Figure 10).

24. Counseling for genetic testing of embryos

cryopreservation, donation, research) should be discussed.

bodies as there are fewer traumas to the oocyte.

non-invasive.

92 Genetic Diversity and Disease Susceptibility

use of donor gametes).

biopsy.

25. Polar body biopsy

Blastomere biopsy can be obtained at day 3 embryos. Blastocyst biopsy can be done on Day 5 or Day 6 embryos.

Blastomere biopsy is done by zona drilling with acid Tyrode solution or mechanical aspiration. Alternatively laser denudation can be done. If removal of two cells is considered it should be done only after an embryo has six or more cells. Blastomere biopsy is associated with low implantation rates [24].

Blastocyst biopsy on Day 5 or Day 6 embryos is done with noncontact infrared lasers. Laser is used to create an opening in the zona pellucida and the herniating trophectoderm is excised. Around 10 trophectoderm cells are removed and studied. Blastocyst biopsy of trophectoderm does not lead to reduced implantation and delivery rates. It should be remembered that the RCTs that demonstrated a beneficial effect of embryo biopsy were only done on blastocyst stage with trophectoderm biopsy.
