Embryo selection versus natural selection How do outcomes of comprehensive chromosome screening of blastocysts compare with the analysis of products of conception from early pregnancy loss dilation and curettage among an assisted reproductive technology population

Capsule:
This study compares the incidence of numerical chromosomal abnormalities reported after preimplantation genetic screening analysis vs. those reported after cytogenetic analysis of products of conception after spontaneous abortion.

Authors:
Jorge Rodriguez-Purata, M.D., Joseph Lee, B.A., Michael Whitehouse, B.A., Rose Marie Moschini, M.S., Jaime Knopman, M.D., Marlena Duke, M.S., Benjamin Sandler, M.D., Alan Copperman, M.D.

Volume 104, Issue 6, Pages 1460-1466

Abstract:

Objective:
To compare the incidence of numerical chromosomal abnormalities (NCAs) reported after preimplantation genetic screening (PGS) analysis compared with that reported after cytogenetic analysis of products of conception after spontaneous abortion.

Design:
Retrospective study.

Setting:
Private academic in vitro fertilization center.

Patient(s):
Cytogenetic reports of patients who underwent an IVF cycle with PGS of at least one biopsied embryo were compared with cytogenetic analysis reported from patients who had dilation and curettage (D&C) for the treatment of a spontaneous abortion after assisted reproductive technology (ART) treatment.

Intervention(s):
None.

Main Outcome Measure(s):
Frequencies for each numerical chromosomal abnormality from both groups were compared.

Result(s):
A total of 1,069 NCAs were reported after PGS (trisomy 54.3%, monosomy 45.7%, no polyploidies), resulting in a trisomy/monosomy ratio of 0.82. A total of 447 NCAs was reported after D&C (trisomy 83%, polyploidy 10.7%, monosomy 6.3%). The aneuploidies most frequently identified were similar in both groups and included 15, 16, 18, 21, and 22. Monosomies (n = 28, 6.3%) were rarely observed in the group that underwent D&C after ART.

Conclusion(s):
This review provides an analysis of the most commonly identified NCAs after PGS and in first-trimester D&C samples in an infertile population utilizing ART. Although monosomies comprised >50% of all cytogenetic anomalies identified after PGS, there were very few identified in the post-D&C samples. This suggests that although monosomies occur frequently in the IVF population, they commonly do not implant. Despite this difference, this study demonstrated that the specific NCAs observed after PGS analysis and D&C were comparable.

  • Mario Gilberto Vega, MD

    Dear Dr. Rodriguez-Purata,

    Thank you for such a valuable contribution. In my opinion this paper adds to the growing body of evidence that A. There may be an over diagnosis of monosomies with current PGS technologies (Gleicher reported at ASRM on transferred monosomic embryos that resulted in healthy neonates) or B. monosomic embryos do not have the same implantation potential. After your review of the literature for your paper and your findings would you suspect one hypothesis over the other?

    Thank you,

    • jorgerdzpurata

      Thank you so much Mario for your interest in our study. I think that definitely monosomic embryos have a reduced implantation potential when compared to trisomic embryos, it would actually be very interesting to know why and if the loss of certain chromosomes are correlated to even lower implantation that others. For instance, we know that chromosome X, X are correlated to XXX, which is supported by our results.
      On the other hand, we are definitely seeing an over utilization of PGS techniques, which then is traduced in over – or more exactly mis – diagnosis.

    • jorgerdzpurata

      Thank you so much Mario for your interest in our study. I think that definitely monosomic embryos have a reduced implantation potential when compared to trisomic embryos, it would actually be very interesting to know why and if the loss of certain chromosomes are correlated to even lower implantation than others. On the other hand, more than an over diagnosis its more an over utilization of PGS techniques, which then is traduced in over – or more exactly – mis diagnosis. After conducting this study we think that PGS certainly help us reducing certain implantation failures by eliminating from the available cohort those embryos that are monosomic and will never implant, but on the other hand we are definitely seeing an increasing number of patients that do not reach the blastocyst/biopsy stage and end up without a transfer. Like you said, it adds to the growing body of evidence and at the same time it helps patients understand why sometimes a transfer do not result in an implantation, specially after the transfer of an unscrened embryo(s).
      Thank you,

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