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categories: ["reproduction", "genetics", "society"]categories: ["reproduction", "genetics", "society"]tags: ["polygenic scores", "ivf", "embryo selection", "genomics", "bioethics", "reproduction"]tags: ["polygenic scores", "ivf", "embryo selection", "genomics", "bioethics", "reproduction"]summary: "The ranking of IVF embryos by polygenic risk scores computed from their inferred genotypes, sold commercially since 2019 and rejected as unvalidated by professional genetics bodies."summary: "The ranking of IVF embryos by polygenic risk scores computed from their inferred genotypes, sold commercially since 2019 and rejected as unvalidated by professional genetics bodies."updated: "2026-07-27"updated: "2026-08-23"humanEvidence: "Children have been born after polygenic ranking of embryos, but no study has followed selected children to test the predicted gain; the scores are validated in adult cohorts, mostly of European ancestry."humanEvidence: "Children have been born after polygenic ranking of embryos, but no study has followed selected children to test the predicted gain; the scores are validated in adult cohorts, mostly of European ancestry."access: "Sold in the United States as a laboratory-developed test, an add-on to a self-funded IVF cycle at a small number of clinics; the United Kingdom does not permit it and several European states restrict it."access: "Sold in the United States as a laboratory-developed test, an add-on to a self-funded IVF cycle at a small number of clinics; the United Kingdom does not permit it and several European states restrict it."reversibility: "irreversible"reversibility: "irreversible"lines 43–48 → 43–5228 unchanged lines not shown
## How it works## How it works PGT-P attaches to an existing clinical workflow rather than replacing it. Five or six days after fertilisation, an embryologist biopsies five to ten cells from the trophectoderm, the outer layer of the blastocyst that will become placenta rather than fetus. The DNA in that sample is measured in picograms, so it is first amplified across the whole genome, then read on a SNP array or by low-pass sequencing.PGT-P attaches to an existing clinical workflow rather than replacing it. Five or six days after fertilisation, an embryologist biopsies five to ten cells from the trophectoderm, the outer layer of the blastocyst that will become placenta rather than fetus. The DNA in that sample is measured in picograms, so it is first amplified across the whole genome, then read on a SNP array or by low-pass sequencing. ```figure{"key": "blastocyst-day-five", "caption": "A day-5 blastocyst, the stage at which five to ten trophectoderm cells are biopsied. The sampled outer layer becomes placenta, not fetus — the entire genetic report rests on picograms of DNA from those few cells."}``` The resulting genotype is sparse and noisy. To make a polygenic score usable, the laboratory imputes the missing variants: it genotypes both parents, reconstructs which parental haplotypes each embryo inherited, and fills in the rest by reference to a haplotype panel. An embryo's score is therefore not measured but reconstructed, and imputation error propagates into the ranking. Companies then sum the embryo's variant dosages weighted by effect sizes taken from a published genome-wide association study, and report each embryo's position relative to its siblings or to a population distribution.The resulting genotype is sparse and noisy. To make a polygenic score usable, the laboratory imputes the missing variants: it genotypes both parents, reconstructs which parental haplotypes each embryo inherited, and fills in the rest by reference to a haplotype panel. An embryo's score is therefore not measured but reconstructed, and imputation error propagates into the ranking. Companies then sum the embryo's variant dosages weighted by effect sizes taken from a published genome-wide association study, and report each embryo's position relative to its siblings or to a population distribution. removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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