Genetic diseases and aneuploidies can be detected with a single blastocyst biopsy: a successful clinical approach.
Can simultaneous detection of aneuploidies and genetic diseases or chromosomal aberrations in blastocysts reduce the chance of transferring embryos with low implantation potential, guaranteeing good clinical outcomes?
The screening for chromosomal aneuploidies revealed that 50.6% of blastocysts diagnosed free of genetic disease or balanced, were aneuploid, therefore avoiding the transfer of blastocysts potentially resulting in implantation failures, miscarriages, or in some cases, in health affected live births.
PGD is applied in patients at risk of transmitting genetically inheritable diseases to their offspring. It has been demonstrated that aneuploidies can involve chromosomes other than those investigated with PGD, affecting embryo implantation competence. Performing the biopsy at blastocyst level produces higher clinical outcomes allowing a more accurate diagnosis, compared to blastomere biopsy.
This consecutive case series study was performed from October 2011 to May 2016. Clinical and biological outcomes from 1122 blastocysts obtained in 304 PGD cycles for monogenic diseases (N = 163) or chromosomal rearrangements (N = 141) were analyzed. When the blastocyst resulted transferable after the PGD analysis or chromosomal rearrangement analysis, its ploidy status by mean of preimplantation genetic screening (PGS) was also detected using the same biopsy sample. Mean female age was 35.4 ± 4.2 years old. All biopsies were performed at blastocyst stage and analyzed by Whole Genome Amplification (WGA) followed by PCR for monogenic diseases, and by array-comparative genotype hybridization (array-CGH) for all cycles.
All mature oocytes retrieved were injected and cultured individually until the blastocyst stage at 37°C, 6% CO2, 5% O2. When the blastocyst was formed, it was biopsied and vitrified, awaiting the genetic results. The frozen-thawed embryo transfer was performed in a subsequent cycle. In some cases, when the blastocyst was obtained within the morning of Day 5 of culture, it had been maintained in culture and transferred on Day 6, after receiving the genetic report.
A total of 2809 (2718 fresh and 91 frozen-thawed) mature oocytes were injected with a fertilization rate of 75.5% (N = 2120), leading to the development of 2102 embryos. A further 24 frozen embryos, previously vitrified without any genetic testing, were successfully warmed for genetic screening. A total of 2126 embryos were cultured with a blastocyst formation rate of 52.8% (N = 1122); all of them were biopsied from Day 4 to Day 7 of culture. After the genetic analysis, 309 (27.5%) blastocysts resulted transferable, both for monogenic disease or translocation and for their ploidy status, 42 were diploid/aneuploid mosaic, 55 were no result and 716 were not transferable, due to genetic disease or chromosomal rearrangement and/or for their ploidy status. Of note, 316 (50.6% of transferable blastocysts after PGD and 28.2% of total number of biopsied blastocysts) of the blastocysts resulted healthy for the genetic disease or chromosomal rearrangement were aneuploid. Out of 304 PGD/PGS cycles performed, 28.6% (N = 87) resulted in no-transferable blastocysts after only PGD analysis; this percentage increased to 39.8% (N = 121) when also PGS was carried out (Mc Nemar test P < 0.001). A total of 202 embryo-transfers were performed, 53 fresh and 149 cryopreserved, in which 218 healthy or carrier euploid blastocysts were transferred. Clinical pregnancy, implantation and miscarriage rates were 49.0, 47.7 and 9.9%, respectively. To date, 66 deliveries occurred with 70 healthy babies born and 13 pregnancies are still ongoing. Finally, 91 euploid healthy blastocysts are still cryopreserved waiting to be transferred.
A higher than expected cycle cancellation rate could be found due to the double genetic analysis performed. For this reason, particular care should be taken in drafting and explaining informed consent, in order to avoid patient drop out.
When the biopsy has to be performed in order to prevent the transmission of an inheritable disease, it should be mandatory to analyze also the genetic status of the blastocyst, avoiding useless embryo-transfers in this particular category of patients. In our study, 316 aneuploid healthy blastocysts could have been transferred without performing PGS, leading to implantation failures, miscarriages, or in some cases, to live births affected by different syndromes.
No specific funding was obtained for this study. None of the authors have any competing interests to declare.
Not applicable.
Minasi MG
，Fiorentino F
，Ruberti A
，Biricik A
，Cursio E
，Cotroneo E
，Varricchio MT
，Surdo M
，Spinella F
，Greco E
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Diminished effect of maternal age on implantation after preimplantation genetic diagnosis with array comparative genomic hybridization.
To assess the relationship between maternal age, chromosome abnormality, implantation, and pregnancy loss.
Multicenter retrospective study.
IVF centers in the United States.
IVF patients undergoing chromosome screening.
Embryo biopsy on day 3 or day 5/6 with preimplantation genetic diagnosis (PGD) by array comparative genomic hybridization.
Aneuploidy, implantation, pregnancy, and loss rates.
Aneuploidy rates increased with maternal age from 53% to 93% for day 3 biopsies and from 32% to 85% for blastocyst biopsies. Implantation rates for euploid embryos for ages <35-42 years did not decrease after PGD: ranges 44%-32% for day 3 and 51%-40% for blastocyst. Ongoing pregnancy rates per transfer did not decrease for maternal ages <42 years after PGD with day 3 biopsy (48.5%-38.1%) or blastocyst biopsy (64.4%-54.5%). Patients >42 years old had implantation rates of 23.3% (day 3), 27.7% (day 5/6), and the pregnancy rate with day 3 biopsy was 9.3% and with day 5 biopsy 10.3%.
Selective transfer of euploid embryos showed that implantation and pregnancy rates were not significantly different between reproductively younger and older patients up to age 42 years. Some patients who start an IVF cycle planning to have chromosome screening do not have euploid embryos available for transfer, a situation that increases with advancing maternal age. Mounting data suggests that the dramatic decline in IVF treatment success rates with female age is primarily caused by aneuploidy.
Harton GL
，Munné S
，Surrey M
，Grifo J
，Kaplan B
，McCulloh DH
，Griffin DK
，Wells D
，PGD Practitioners Group
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ResearchGate
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