The study showed that the size of the embryo cohort does not affect the rate of normal embryos identified by PGD. The authors used array CGH to evaluate embryos on day 3 and day 5. The study was retrospective using data from a PGD reference lab. They studied 7753 embryos from 990 patients.
Embryo Cohort Findings
First, we see the expected decline in chromosomally normal embryos with age. Note that the incidence of normal embryos are higher on day 5 as many abnormal embryos do not survive the time in culture.
We might expect a higher rate of normal embryos when we biopsy a larger embryo cohort. If a woman produces more embryos then perhaps she produces better embryos. This study suggests that premise is not true. If we use genetics as a measure of good, then the incidence of chromosomally normal embryos does not vary by the size of the embryo cohort.
The study also shows a very high rate of at least 1 normal embryo after day 5 embryo biopsy. If there were <5 embryos biopsied then we see fewer women with at least 1 normal embryo. This data could lead to more accurate eSET. This study only looked at embryo genetics. Thus,we cannot say what the effect would have been on pregnancy rates and deliveries. Nevertheless, the data are compelling for more study.
Great article showing the incidence of euploidy (using CGH) in embryos biopsied on day 3 or day 5. The size of the embryo cohort biopsied did not affect the incidence of normal embryos. The study also gives us some idea of the usefulness of CGH PGD for identifying the single embryo to transfer.
The authors of this article are known for numerous high quality studies regarding PGD.