Advantages and Disadvantages of Polar Body Biopsy

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The advantages of polar body biopsy are that, first, it is ethically more acceptable to certain countries (e.g., Malta and Germany) where research and discarding embryos is prohibited. Second, the first and second polar bodies may not be required for further embryonic development and hence the viability of the oocytes and resulting embryos may be equally maintained.

One disadvantage of polar body biopsy is that it can only be applied to diagnose maternally inherited diseases. Recombination and post zygotic events leading to chromosomal abnormalities cannot be detected by this method. Diseases that are detected by assessing changes in gene product are also impossible, as well as gender determination (sexing).

Advantages Polar Bodies
Figure 6.1. Polar body biopsy. (a) A hole is made in the zona pellucida using a laser; (b) the aspiration pipette is placed near the hole; (c) the polar body is aspirated; (d) polar body and biopsied oocyte.

Another disadvantage is that the oocyte/zygote is subjected to two manipulations in cases of sequential biopsy of the first and second polar body rather than to a single manipulation at the cleavage stage. In addition, ICSI has to be carried out in between regardless of the type of diagnosis, as insemination by IVF could lead to polyspermy and sperm contamination for PCR diagnosis. Cleavage-stage biopsy of embryos derived from these manipulated zygotes has also been reported to confirm diagnosis (38). This is highly labor intensive and can be detrimental to the embryo.

A third disadvantage is that, in cases where the first and second polar bodies are removed at the same time in one manipulation, the first polar body degenerates between the time of oocyte retrieval and biopsy following fertilization (34). This may lead to failure of diagnosis in the first polar body due to fragmenting or degenerating DNA. The biopsy of only the first polar body would lead to an overall lower reliability of diagnosis, as only one cell is available for analysis, in contrast to cleavage stages, where up to two cells can be taken for independent testing. In addition, it is thought that the risk of misdiagnosis is greater from polar bodies than from blastomeres (43). Finally, sometimes the first polar body is not very well detached from the oolema, which can lead to lysis during the biopsy procedure.

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