25. Polar body biopsy

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 biopsy.

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 bodies as there are fewer traumas to the oocyte.

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 bodies 10% will be due to nondisjunction and the remaining 45% from half of the premature separation of sister chromatids.
