Using outcome data from one thousand mosaic embryo transfers to formulate an embryo ranking system for clinical use

Fertil Steril. 2021 May;115(5):1212-1224. doi: 10.1016/j.fertnstert.2020.11.041. Epub 2021 Mar 6.


Objective: To study how the attributes of mosaicism identified during preimplantation genetic testing for aneuploidy relate to clinical outcomes, in order to formulate a ranking system of mosaic embryos for intrauterine transfer.

Design: Compiled analysis.

Setting: Multi-center.

Patient(s): A total of 5,561 euploid blastocysts and 1,000 mosaic blastocysts used in clinical transfers in patients undergoing fertility treatment.

Intervention(s): None.

Main outcome measure(s): Implantation (gestational sac), ongoing pregnancy, birth, and spontaneous abortion (miscarriage before 20 weeks of gestation).

Result(s): The euploid group had significantly more favorable rates of implantation and ongoing pregnancy/birth (OP/B) compared with the combined mosaic group or the mosaic group affecting only whole chromosomes (implantation: 57.2% vs. 46.5% vs. 41.8%; OP/B: 52.3% vs. 37.0% vs. 31.3%), as well as lower likelihood of spontaneous abortion (8.6% vs. 20.4% vs. 25%). Whole-chromosome mosaic embryos with level (percent aneuploid cells) <50% had significantly more favorable outcomes than the ≥50% group (implantation: 44.5% vs. 30.4%; OP/B: 36.1% vs. 19.3%). Mosaic type (nature of the aneuploidy implicated in mosaicism) affected outcomes, with a significant correlation between number of affected chromosomes and unfavorable outcomes. This ranged from mosaicism involving segmental abnormalities to complex aneuploidies affecting three or more chromosomes (implantation: 51.6% vs. 30.4%; OP/B: 43.1% vs. 20.8%). Combining mosaic level, type, and embryo morphology revealed the order of subcategories regarding likelihood of positive outcome.

Conclusion(s): This compiled analysis revealed traits of mosaicism identified with preimplantation genetic testing for aneuploidy that affected outcomes in a statistically significant manner, enabling the formulation of an evidence-based prioritization scheme for mosaic embryos in the clinic.

Keywords: IVF; Next-Generation Sequencing; embryo; mosaicism; preimplantation genetic testing.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aneuploidy
  • Blastocyst / classification*
  • Blastocyst / cytology
  • Blastocyst / metabolism
  • Data Interpretation, Statistical
  • Embryo Implantation / genetics
  • Embryo Transfer / statistics & numerical data
  • Embryonic Development / genetics
  • Female
  • Fertilization in Vitro / standards
  • Fertilization in Vitro / statistics & numerical data
  • Genetic Testing / methods
  • Genetic Testing / standards
  • Genetic Testing / statistics & numerical data
  • Humans
  • Infant, Newborn
  • Infertility / diagnosis
  • Infertility / epidemiology
  • Infertility / genetics
  • Infertility / therapy
  • Karyotyping / methods
  • Karyotyping / standards
  • Karyotyping / statistics & numerical data
  • Male
  • Mosaicism / embryology*
  • Pregnancy
  • Pregnancy Outcome / epidemiology
  • Pregnancy Outcome / genetics
  • Pregnancy Rate
  • Preimplantation Diagnosis / methods*
  • Preimplantation Diagnosis / standards
  • Preimplantation Diagnosis / statistics & numerical data
  • Prognosis
  • Treatment Outcome