Postfertilization telomere marker testing in human embryos: a pilot study of a novel embryo evaluation assay

To determine whether telomere measurement (Teloscore) derived from sequencing data from preimplantation genetic testing for aneuploidy (PGT-A) improves embryo selection beyond morphology and ploidy assessment alone in assisted reproduction.

Retrospective cohort study.

A total of 5,251 blastocysts from 1,451 couples undergoing in vitro fertilization/PGT-A cycles between September 2023 and February 2025 (mean maternal age, 36.5 years) were included.

Teloscore, derived from reanalysis of routine PGT-A sequencing data and quantified as telomeric reads per million total reads.

Implantation after single embryo transfer (SET), defined as the presence of a gestational sac.

Among 335 SET cycles (development cohort: 234; validation cohort: 101), implantation occurred in 206 cases (61.5%). Teloscore independently predicted implantation in the multivariable logistic regression model (odds ratio [OR]: 1.096 per unit increase, 95% confidence interval [CI]: 1.011-1.188), along with day 5 biopsy (OR: 1.993, 95% CI: 1.071-3.707). Findings were consistent in both the development and validation cohorts. A predictive model incorporating Teloscore, biopsy timing, body mass index, and embryo morphology yielded an area under the curve of 0.668, which was replicated in the validation cohort (0.634). Implantation rates rose progressively with increasing Teloscore, from 36.8% (0-4) to 63.3% (4-7), 64.6% (7-10), 65.7% (10-13), and 72.4% (≥13). Technical reproducibility was confirmed using duplicate sequencing runs (R² = 0.756).

The Teloscore, derived from reanalysis of routine PGT-A data, is a feasible, reproducible, and cost-effective biomarker for embryo assessment. At this stage, rather than offering a definitive clinical test, the Teloscore provides a hypothesis-generating framework that suggests telomere recovery may be linked to embryonic competence and implantation potential. Its integration into current workflows offers an opportunity to explore telomere biology as a complementary approach in embryo selection.