ESHRE PGT Consortium and SIG Embryology good practice recommendations for polar body and embryo biopsy for PGT.

The field of preimplantation genetic testing (PGT) is evolving fast, and best practice advice is essential for regulation and standardisation of diagnostic testing. The previous ESHRE guidelines on best practice for PGD, published in 2005 and 2011, are considered outdated, and the development of new papers outlining recommendations for good practice in PGT was necessary.The current paper provides recommendations on the technical aspects of embryo biopsy and covers recommendations on the biopsy procedure, cryopreservation and laboratory issues and training, in addition to technical aspects and strengths and limitations specific for currently used techniques at different stages (polar body, cleavage stage and blastocyst biopsy). Furthermore, alternative sampling methods are briefly described.This paper is one of a series of four papers on good practice recommendations on PGT. The other papers cover the organisation of PGT, and the different technical aspects of PGT for monogenic/single-gene defects (PGT-M) and PGT for chromosomal structural rearrangements/aneuploidies (PGT-SR/PGT-A).Together, these papers should assist everyone interested in PGT in developing the best laboratory and clinical practice possible.