David Roy Meldrum, M.D., H. Irene Su, M.D., M.S.C.E., Mandy G. Katz-Jaffe, Ph.D., William B. Schoolcraft, M.D.
In this issue Kushnir et al. (1) recalculated Centers for Disease Control data reporting 2011–2012 fresh cycle preimplantation genetic screening (PGS) live birth rates per ET. They appropriately pointed out that PGS results must be reported per initiated cycle. Increased live birth rates per ET may result from excluding from ET embryos destined to not implant or miscarry. They concluded that nationwide improvements in live birth and miscarriage rates reported for older women were “likely due to favorable patient selection biases.” However, this data set was not optimally analyzed by intention to treat (i.e., cycle start), because only cycles with at least one oocyte retrieved were included and approximately 40% of cycles did not reach transfer for various reasons including “freeze all” or cycles with no euploid embryo (Chang J, personal communication, 2016).
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