Study: Segmental Aneuploid Embryos Yield
A large study found embryos with whole chromosome abnormalities resulted in zero live births, while those with segmental abnormalities had a 17.1% success
A major study found a stark difference in outcomes between two types of genetically abnormal embryos used in IVF. According to research published in Fertility and Sterility on September 1, 2026, embryos classified as having whole chromosome aneuploidy produced no live births, while those with segmental aneuploidy resulted in a 17.1% live birth rate.
The findings come from a large, multicenter retrospective cohort study led by the International Registry of Mosaic Embryo Transfers (IRMET) network. Data was collected from eight fertility centers between 2016 and 2026. The analysis included 250 embryo transfers where embryos had been classified by preimplantation genetic testing for aneuploidy (PGT-A). Of these, 168 were whole chromosome aneuploid (WCA) and 82 were segmental aneuploid (SA).
No Live Births from Whole Chromosome Aneuploid Embryos
Researchers observed a complete absence of live births from the 168 transfers of embryos with whole chromosome abnormalities. This result held true even for the 111 transfers performed without the clinic's prior knowledge of the PGT-A result. The study's authors, including lead researcher Manuel Viotti, Ph.D., noted that most of these transfers simply failed to result in a pregnancy.
Outcomes for the WCA embryo transfers broke down as follows:
| Outcome | Percentage of Transfers |
|---|---|
| No Pregnancy | 78.6% |
| Biochemical Pregnancy | 8.3% |
| Ectopic Pregnancy | 1.8% |
| Early Spontaneous Abortion | III9.5% |
| Late Spontaneous Abortion | 1.2% |
| Therapeutic Termination | 0.6% |
Live Birth Success with Segmental Abnormalities
In direct contrast, transfers involving embryos with segmental aneuploidies showed a clinically meaningful potential for success. From 82 SA embryo transfers, the live birth rate was 17.1%. The researchers reported that neonatal data was available for 10 of these live births.
Those babies showed no differences in gestational age or birthweight compared to infants born from euploid embryo transfers at the same clinics. Also, all cases where prenatal or neonatal genetic testing was performed returned normal results.
Implications for IVF and PGT-A
The study provides strong support for the biological validity of PGT-A classifications. It clearly distinguishes between whole chromosome and segmental abnormalities. The data suggests that embryos with uniform whole chromosome aneuploidy have no potential for a live birth. Segmental aneuploid embryos, however, retain a modest chance.
This has significant implications for clinical decision-making in fertility treatment. The findings help clarify the distinct clinical implications of different genetic test results. For patients and clinicians navigating complex IVF choices, this information is vital.
The research involved a consortium of international fertility centers. Data was gathered from clinics in North America, Europe, and Australia. All embryos were biopsied at the blastocyst stage and analyzed using next-generation sequencing.
