MOSAIC PGT-A RESULTS

Jennifer Luque, MGC, CGC (she/her)

Certified Genetic Counselor

jennifer.luque@coopersurgical.com

Disclosures

• I am a full time employee of CooperSurgical with the Donor Gamete team (California Cryobank and Donor Egg Bank USA).
• I am a former employee of CooperGenomics (previously Reprogenetics).

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Credit due to Meaghan Doyle, MS, CGC of DNAide, who generously shared slide resources for this presentation.

Learning Objectives

• Explore the latest developments regarding mosaic results from PGT-A testing of embryo biopsies.

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Outline

• Preimplantation genetic testing for aneuploidy (PGT-A)
• Mosaic PGT-A Results
• Transfer following mosaic results
• Currently available outcome data
• Prenatal management guidance

�PGT-A

Preimplantation Genetic Testing for Aneuploidy

Trophectoderm Biopsy

Video courtesy of RGI

Current methodology - NGS

Image modified from CooperGenomics

MOSAIC PGT-A RESULTS

Mosaic results, not mosaic embryos

Traditional diagnoses of mosaicism

Mosaic PGT-A results via NGS

46, XX, -3[mos], +22[mos]

aCGH vs NGS

Image courtesy of CooperGenomics

Variables in mosaicism calling

ASRM Committee Opinion, 2023

Reporting thresholds are variable

• Not uncommon for reporting practices to change over time
• Thresholds may be different for whole chromosome compared to segmental aneuploidies
• Some technologies can detect triploidy/polyploidy and others can’t

Lab One

Euploid: <20%

Low mosaic: 20-40%

High mosaic: 41-80%

Aneuploid: >80%

Lab Two

Euploid: <20%

Mosaic: 20-40%

Aneuploid: 41-80%

Lab Three

Euploid: <30%

Low level: 30-50%

High level: 51-70%

Aneuploid: >70%

Limitations to interpretation

• Extrapolating from biopsy sample to entire embryo
• Distinguishing low level mosaicism from noise
• Laboratory specific call policies
• Variability across clinics/embryologists

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Vera-Rodriguez and Rubio, 2017

TRANSFER OUTCOMES

Mosaic Embryo Transfer (MET)

Prenatal vs PGT-A

• Mosaic aneuploidies involving nearly every chromosome have been associated with abnormal phenotypes in pregnancies and live births, regardless of the method of conception
• Mosaic PGT-A results have thus far not been definitively associated with a significantly increased risk of an adverse fetal or neonatal outcome

Mosaic outcomes data

• In general, embryos with mosaic results are expected to implant less often and miscarry more often than embryos with euploid results
• ~2,700 documented mosaic embryo transfers across various studies
• Retrospective
• Prospective
• <1% risk of persisting mosaicism
• About 7 cases in the literature of persisting mosaicism or aneuploidy in an ongoing pregnancy after MET
• More data needed

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Most likely outcomes of mosaic embryo transfer

• No implantation
• Early pregnancy loss
• Healthy live birth

Mosaic PGT-A results are more likely to impact the chance of getting pregnant and staying pregnant through the first trimester, rather than the health of the baby

• PGT-A result: mosaic monosomy 2
• Amnio: 46,XX(98)/47,XX,+2(2)
• Normal ultrasounds, no IUGR
• Healthy live birth at 37 weeks
• Peripheral blood karyotyping: 45,XX,-2(2)/46,XX(98)

Case 1 of 3

• PGT-A result: mos (+1q, -7, -8, +9,-19, -20, +21) [40%]
• CVS karyotype G-banding (mos +21, 80%),
• CVS array (mos +21),
• Amnio karyotype and FISH (mos +21, 16%)
• 19 week ultrasound showed severe anomalies
• Pregnancy was terminated

• 172 singleton births from PGT-A tested embryos revisited at 3 years of age
• 115 with euploid results, 57 with low level (25-50%) mosaic results
• No significant differences in newborn measures or postnatal outcomes

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Morales et al., 2024

WHAT IS HAPPENING IN THESE EMBRYOS?

Getting theoretical

Theory #1: Location of aneuploid cells

ICM is euploid

ICM is aneuploid

ICM is mosaic

Most embryos with initial low mosaic PGT-A results had no other signs of mosaicism/

aneuploidy in the rest of the embryo

Theory #2: Self-correction

Abnormal cells die off

Healthy cells grow quickly and compensate

• 80 blastocysts (day 5 or 6)
• Grown in conditions replicating the maternal environment
• Cultured to day 8 or 12
• Assessed if they were still attached and the PGT-A results

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• 58% (7 of 12) mosaics were still viable by day 12
• 5 of 7 were chromosomally normal by day 12

Theory #3: PGT result inaccuracies

• Potential false positive
• Trophectoderm biopsy was never mosaic to begin with

DISPOSITION AND PRIORITIZATION

We’ve got this mosaic result…what do we do with the embryo?

Prioritization guidance – PGDIS 2016

Prioritization guidance - PGDIS 2021

• Low level mosaics over high level mosaics
• Segmental over whole chromosome
• Chromosomes involved
• If all else equivocal, defer to embryo morphology

Common considerations

Patient

• Reproductive history
• Availability of additional embryos
• Age of egg source
• Financial costs

Clinician

• Clinician counseling
• Opinion r/e mosaic results
• Professional background
• Clinic policies
• Mosaic transfer
• Mosaic storage

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AND THEN WHAT?

Prenatal management

Committee Opinions and Statements

• SOGC 2019: MMS and NIPT are not recommended. Invasive diagnostic testing is strongly recommended, with amniocentesis strongly preferred over CVS
• ACOG 2020: Prenatal diagnosis with CVS or amniocentesis should be strongly considered
• ACMG 2020: Prenatal UPD testing after mosaic embryo transfer for embryos with mosaic monosomy or trisomy for chromosomes 6, 7, 11, 14, 15 or 20
• ASRM 2023: Currently there is a lack of data to inform evidence-based recommendations for prenatal testing after mosaic embryo transfer

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2023

• Patients should be counseled that screening tests do not diagnose aneuploidy
• Ultrasound/biochemical analytes identify congenital anomalies that may be associated with aneuploid pregnancy
• Many aneuploidies (especially when mosaic) may not result in visible ultrasound anomalies or skewed biochemical analytes

NIPT

• Tests placental DNA
• Risk of confined placental mosaicism
• Most NIPT tests available:
• Aren’t validated to detect mosaicism
• Test for a select number of whole chromosome aneuploidies
• Prenatal diagnosis is recommended to confirm a positive result

• CVS tests placental DNA
• Risk of confined placental mosaicism
• Amniocentesis tests fetal DNA
• Can detect true fetal mosaicism and aneuploidy
• Mosaicism can be missed
• If not present in the sample
• If present at a low level

CVS & Amnio

Analysis on prenatal samples

• Karyotype
• Consider additional cell count
• FISH
• Chromosomal microarray
• UPD studies

Considerations

• Risk of persisting mosaicism/aneuploidy is low but not zero
• Results may or may not be related to initial PGT-A result
• More cases of incidental findings have been reported than true persisting mosaicism or aneuploidy related to the mosaic PGT-A result
• Ultrasound anomalies + fetal mosaicism is easier to interpret than fetal mosaicism in the absence of ultrasound anomalies

References

Barad, D. H., Albertini, D. F., Molinari, E., & Gleicher, N. (2022). IVF outcomes of embryos with abnormal PGT-A biopsy previously refused transfer: a prospective cohort study. Human reproduction (Oxford, England), 37(6), 1194–1206. https://doi.org/10.1093/humrep/deac063

Capalbo, A., Poli, M., Rienzi, L., Girardi, L., Patassini, C., Fabiani, M., Cimadomo, D., Benini, F., Farcomeni, A., Cuzzi, J., Rubio, C., Albani, E., Sacchi, L., Vaiarelli, A., Figliuzzi, M., Findikli, N., Coban, O., Boynukalin, F. K., Vogel, I., Hoffmann, E., … Simón, C. (2021). Mosaic human preimplantation embryos and their developmental potential in a prospective, non-selection clinical trial. American journal of human genetics, 108(12), 2238–2247. https://doi.org/10.1016/j.ajhg.2021.11.002

Cheng, L., Meiser, B., Kennedy, D., Kirk, E., Barlow-Stewart, K., & Kaur, R. (2022). Exploration of decision-making regarding the transfer of mosaic embryos following preimplantation genetic testing: a qualitative study. Human reproduction open, 2022(4), hoac035. https://doi.org/10.1093/hropen/hoac035

Del Gaudio, D., Shinawi, M., Astbury, C., Tayeh, M. K., Deak, K. L., Raca, G., & ACMG Laboratory Quality Assurance Committee (2020). Diagnostic testing for uniparental disomy: a points to consider statement from the American College of Medical Genetics and Genomics (ACMG). Genetics in medicine : official journal of the American College of Medical Genetics, 22(7), 1133–1141. https://doi.org/10.1038/s41436-020-0782-9

Kahraman, S., Cetinkaya, M., Yuksel, B., Yesil, M., & Pirkevi Cetinkaya, C. (2020). The birth of a baby with mosaicism resulting from a known mosaic embryo transfer: a case report. Human reproduction (Oxford, England), 35(3), 727–733. https://doi.org/10.1093/humrep/dez309

Popovic, M., Dhaenens, L., Taelman, J., Dheedene, A., Bialecka, M., De Sutter, P., Chuva de Sousa Lopes, S. M., Menten, B., & Heindryckx, B. (2019). Extended in vitro culture of human embryos demonstrates the complex nature of diagnosing chromosomal mosaicism from a single trophectoderm biopsy. Human reproduction (Oxford, England), 34(4), 758–769. https://doi.org/10.1093/humrep/dez012

Practice Committee and Genetic Counseling Professional Group (GCPG) of the American Society for Reproductive Medicine. Electronic address: asrm@asrm.org (2020). Clinical management of mosaic results from preimplantation genetic testing for aneuploidy (PGT-A) of blastocysts: a committee opinion. Fertility and sterility, 114(2), 246–254. https://doi.org/10.1016/j.fertnstert.2020.05.014

Preimplantation Genetic Testing: ACOG Committee Opinion, Number 799. (2020). Obstetrics and gynecology, 135(3), e133–e137. https://doi.org/10.1097/AOG.0000000000003714

Schlade-Bartusiak, K., Strong, E., Zhu, O., Mackie, J., Salema, D., Volodarsky, M., Roberts, J., & Steinraths, M. (2022). Mosaic embryo transfer-first report of a live born with nonmosaic partial aneuploidy and uniparental disomy 15. F&S reports, 3(3), 192–197. https://doi.org/10.1016/j.xfre.2022.05.003

Treff, N. R., & Marin, D. (2021). The "mosaic" embryo: misconceptions and misinterpretations in preimplantation genetic testing for aneuploidy. Fertility and sterility, 116(5), 1205–1211. https://doi.org/10.1016/j.fertnstert.2021.06.027

Viotti, M., Greco, E., Grifo, J. A., Madjunkov, M., Librach, C., Cetinkaya, M., Kahraman, S., Yakovlev, P., Kornilov, N., Corti, L., Biricik, A., Cheng, E. H., Su, C. Y., Lee, M. S., Bonifacio, M. D., Cooper, A. R., Griffin, D. K., Tran, D. Y., Kaur, P., Barnes, F. L., … Spinella, F. (2023). Chromosomal, gestational, and neonatal outcomes of embryos classified as a mosaic by preimplantation genetic testing for aneuploidy. Fertility and sterility, 120(5), 957–966. https://doi.org/10.1016/j.fertnstert.2023.07.022

Zwingerman, R., & Langlois, S. (2020). Committee Opinion No. 406: Prenatal Testing After IVF With Preimplantation Genetic Testing for Aneuploidy. Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstetrique et gynecologie du Canada : JOGC, 42(11), 1437–1443.e1. https://doi.org/10.1016/j.jogc.209.11.069

QUESTIONS?

Jennifer Luque, MGC, CGC

jennifer.luque@coopersurgical.com