Thesis title: Chromosomal, obstetrical, and neonatal outcomes after the transfer of mosaic embryos analyzed by high resolution Next Generation Sequencing
Objective: Expand the information about clinical outcome in pregnancies obtained after the transfer of mosaic embryos. Provide further insight in the management of prenatal diagnosis in pregnancies after PGT-A result of mosaicism.
Setting: Multi-center study
Patient(s): A total of 11.222 euploid blastocysts and 1808 mosaic blastocysts used in clinical transfers in patients undergoing fertility treatment.
Main Outcome Measure(s): Implantation (gestational sac), ongoing pregnancy, birth, spontaneous abortion, length of gestation, and weight at birth.
Result(s): The euploid group had significantly more favorable rates of implantation and ongoing pregnancy/birth (OP/B-R) compared with the combined mosaic group or the mosaic group affecting only whole chromosomes (implantation: 58,8% vs. 47,7% vs 42,0%; OP/B-R: 52,3% vs 37,9% vs 31,7%), as well as higher risk of Miscarriage ( 9,0% vs 19,7% vs 23,4%). Whole chromosome mosaic embryos with low level (<50%) mosaicism had significantly more favorable outcomes than the high level (>50%) group (implantation: 43,6% vs. 26,4%; OP/B: 34,2% vs. 13,6%). Mosaic type (nature of the aneuploidy implicated in mosaicism) affected outcomes, with a significant correlation between number of affected chromosomes and unfavorable outcomes. Length of gestation and weight at birth were evaluated in case-matched subset of pregnancies resulting in non-significant difference in pregnancies obtained after transfer of mosaic and euploid embryos (length of gestation: 266 d vs 268: weight at birth: 3119 g vs 3189 g). Results of prenatal investigation were collected for a total of 249 pregnancies with a total 364 test results including NIPT, CVS, and Amniocentesis. Test results were normal in 95.2% of pregnancies. The remaining 4.8% had abnormal prenatal test, with 2 (0,8%) confirming persistence of mosaicism detected with PGT-A at the blastocyst stage.
Conclusion(s): this study confirmed that percentage and type of mosaicism influence implantation rate, ongoing pregnancy/birth rate and miscarriage rate, and demonstrated that mosaicism ad blastocyst stage, independently of type and percentage, does not influence birth weight and length of gestation. Evaluation of prenatal testing confirmed the importance of prenatal diagnosis after transfer of mosaic embryos.