Polar body diagnosis (PBD): an alternative and supplement to preimplantation diagnosis for single embryo transfer

Polar body diagnosis (PBD) is an accurate but also costly method of genetic preconception diagnosis. It is used mainly in countries with legal restrictions against preimplantation genetic diagnosis (PGD) of cleaved embryos. The lack of mosaicism is its predominant advantage; the limitation to genetic problems of maternal origin is its principal disadvantage. The first polar body (PB1) is removed before fertilization and the second polar body (PB2) (or both PBs together) at the time of fertilization. Mechanical opening of the zona pellucida is the recommended means of obtaining access to the PBs. There are several techniques available for the genetic analysis of PBs, but the most commonly used today are array-CGH and PCR. After biopsy of the PBs, vitrification of pronuclear stages or cleaved embryos/blastocysts and the subsequent transfer of unaffected embryos/blastocysts in artificial warming cycles allow the time window for genetic testing to be expanded. Misdiagnosis in PBD is known anecdotally. The future of PBD is dependent on both the legal situation and the results of urgently needed prospectively randomized studies including both PBD and PID of cleaved embryos and blastocysts. The combination of PBD with trophectoderm PGD might increase the accuracy of both techniques, particularly when the aim is to transfer only one embryo