Blastocyst stage microarray-based genomic screening in improving clinical pregnancy rate and implantation rate

Identification of embryos with the highest implantation potential is a crucial step in IVF. Blastocyst transfer (BT) has been proved to have higher implantation rate and live birth rate than D3 embryo transfer owing to a further embryo selection mechanism. However, morphological grading provides us only part of clue to choosing a best quality blastocyst. As chromosome abnormality plays a role in pregnancy failure for woman of advanced maternal age and repeated implantation failure, it is important to evaluate the chromosome status before BT to reduce miscarriage rate.

Patient Profile

Trophectoderm Biopsy

》On day 4 of embryonic development, the zona pellucida was breached using a laser and transferred to blastocyst medium.

》On day 5 or 6, expanding blastocysts underwent biopsy of herniating trophectoderm cells.

》Aspirated cells were froze at -20℃ and subjected to chromosome analysis with array comparative genomic hybridization (aCGH).

》Biopsied blastocysts were vitrified using Cryotop method.

》Biopsy procedure

Array comparative genomic hybridization (aCGH)

Chromosome Analysis

》Two hundred and twenty-eight blastocysts were analyzed. The results were as follows:

》Although prolonged culture has been accomplished, there were still about 50% blastocysts possessed chromosomal abnormality

Blastocyst Morphology and Aneuploidy Rate

》To examine the relationship of chromosome status and the morphology of blastocyst, aneuploidy rate were analyzed according to the grading of the inner cell mass and trophectoderm, respectively.

》Aneuploidy rate were analyzed according to the blastocyst grading.

》High aneuploidy rate was observed in blastocyst with lower growth rate.

》No obvious relationship between blastocyst morphology and aneuploidy rate.

Age and Aneuploidy Rate

》Patients were classified as 4 groups according to their age to examine the relationship of age and aneuploidy rate.

#: adopting donor’s age for analysis

》As previous report, high aneuploidy rate is related advanced maternal age. Significant differences were observed among ≦30 group and every other group.

Clinical Outcome

》Warmed BT cycles with aCGH (aCGH group) were compared with contemporary group, which aCGH was not performed, and the clinical outcome was listed below:

》In aCGH group, fewer blastocysts were transferred per cycle, resulted in a relatively low multiple pregnancy rate.

》Clinical pregnancy rate was slightly higher in aCGH group, though without significant difference.

Clinical Outcome in 3 aCGH Sub-group

》In aCGH group, patients were grouped into 3 sub-sets: single embryo transfer (eSET), double embryo transfer (DET) and triple embryo transfer (BT).

》In eSET cycles, pregnancy rate could be achieved by means of aCGH in combination with BT.

》Multiple pregnancy rate was successfully reduced in eSET group.

Conclusions

Our preliminary data indicated that blastocyst stage preimplantation chromosome screening could improve implantation rate. Although there was no statistical significant, pregnancy rate was higher in aCGH group. More clinical data was needed for further study.