Embryo Euploidy Research Articles

Effects of maternal age on euploidy rates in a large cohort of embryos analyzed with 24-chromosome single-nucleotide polymorphism–based preimplantation genetic screening

To determine the effect of maternal age on the average number of euploid embryos retrieved during oocyte harvest as part of an invitro fertilization (IVF) cycle, including the probability of retrieving at least one euploid embryo in a cohort (PrE). Retrospective study. Preimplantation genetic screening (PGS) laboratory. Women aged 18 to 48years undergoing IVF treatment. Use of 24-chromosome single-nucleotide polymorphism (SNP)-based PGS of day-3 and day-5 embryo biopsies. Relationships between maternal age and the rate of embryos that tested as euploid (hereafter referred to as "euploid embryos"), the average number and proportion of euploid embryos per IVF cycle, and PrE. We analyzed 22,599 day-3 embryos and 15,112 day-5 embryos. In women aged 27 to 35years, the median proportion of euploid embryos in each cycle remained constant at ∼35% in day-3 biopsies and ∼55% in day-5 biopsies, but it decreased rapidly after age 35. On average, women in their late 20s had four euploid embryos (day 3 or day 5) per cycle, but this number decreased linearly (R(2) ≥ 0.983) after 35years of age. The effect of maternal age on PrE was similar, with a rapid exponential decline (R(2) = 0.986). Across all maternal ages, the euploid proportion and number of embryos per cycle were counterbalanced, so the number of euploid embryos per cycle was the same for day-3 and day-5 biopsies. This suggests that the loss of embryos from day 3 to day 5 was primarily due to aneuploidy. Our results confirm the known inverse relationship between advanced maternal age (>35years) and embryo euploidy, demonstrating that equal numbers of euploid embryos are available at day 3 and day5.

Is oocyte meiotic spindle morphology associated with embryo ploidy? A prospective cohort study

To explore whether an association exists between oocyte meiotic spindle morphology visualized by polarized light microscopy at the time of intracytoplasmic sperm injection and the ploidy of the resulting embryo. Prospective cohort study. Private IVF clinic. Patients undergoing preimplantation genetic screening/diagnosis (n = 113 patients). Oocyte meiotic spindles were assessed by polarized light microscopy and classified at the time of intracytoplasmic sperm injection as normal, dysmorphic, translucent, telophase, or no visible spindle. Single blastomere biopsy was performed on day 3 of culture for analysis by array comparative genomic hybridization. Spindle morphology and embryo ploidy association was evaluated by regression methods accounting for non-independence of data. The frequency of euploidy in embryos derived from oocytes with normal spindle morphology was significantly higher than all other spindle classifications combined (odds ratio [OR] 1.93, 95% confidence interval [CI] 1.33-2.79). Oocytes with translucent (OR 0.25, 95% CI 0.13-0.46) and no visible spindle morphology (OR 0.35, 95% CI 0.19-0.63) were significantly less likely to result in euploid embryos when compared with oocytes with normal spindle morphology. There was no significant difference between normal and dysmorphic spindle morphology (OR 0.73, 95% CI 0.49-1.08), whereas no telophase spindles resulted in euploid embryos (n = 11). Assessment of spindle morphology was found to be independently associated with embryo euploidy after controlling for embryo quality (OR 1.73, 95% CI 1.16-2.60). Oocyte spindle morphology is associated with the resulting embryo's ploidy. Oocytes with normal spindle morphology are significantly more likely to produce euploid embryos compared with oocytes with meiotic spindles that are translucent or not visible.

Euploidy Predictability of Human Blastocyst Inner Cell Mass and Trophectoderm Grading

Background: The selection of viable, potentially normal, embryos is vital to successful embryo transfers. Subjective morphology grading of blastocysts has been the most accepted and reliable standard to judge embryo quality. However, good to excellent embryo development alone does not necessarily insure euploidy. Our objective was to determine if independent quality grades for blastocyst inner cell mass (ICM) and trophectoderm (TE) can predict early embryo euploidy. Secondly, we aimed to develop a comparison chart for preference of blastocyst quality grades utilizing both ICM and TE grades to improve the decision make process. Methods and Findings: Elective TE biopsy patients (n=139) underwent pre implantation genetic screening (PGS) for aneuploidy screening with subsequent embryo cryopreservation. The ICM/TE of day 5 and 6 blastocysts were independently graded (n>1200 blastocysts) from A to C: A=good to excellent, B=fair, and C=poor quality. All blastocysts achieved full blastocoel expansion prior to grading, laser-assisted blastocyst biopsying of the TE and then micro secure vitrification. Euploid embryos were subsequently selected for warming (>30 days post-PGS) and embryo transfer in 2014. Aneuploidy and pregnancy results were stratified by blastocyst grades. Combined quality grades determined an overall blastocyst grade and were further compared to evaluate preferences for euploidy. Chi-square analysis used to determine significance. Results: Independent grade “A” blastocysts resulted in higher (p<0.05) euploidy predictability (56-62%) compared to “B” quality blastocyst (37-43%). Overall blastocyst quality revealed the TE grade was more predictive of euploidy. Upon warming, 100% embryo recovery and survival was achieved applying vitrification. Cumulative implantation and ongoing pregnancy rates were high at 82% and 78% respectively, with an overall low risk of spontaneous abortion (SAB; 5%). When comparing all quality grades of transferred blastocysts, no significance was observed for implantation, ongoing pregnancy or SAB percentages.

Influence of the paternal age on the embryo development and euploidy in embryos analyzed by fish or aCGH

Influence of the paternal age on the embryo development and euploidy in embryos analyzed by fish or aCGH

The cytogenetic constitution of embryos derived from immature (metaphase I) oocytes obtained after ovarian hyperstimulation

To examine the chromosomal content of embryos resulting from metaphase I (MI) oocytes obtained after ovarian hyperstimulation for IVF. Prospective cohort study. University-based IVF Center, Assaf Harofeh Medical Center, Tel Aviv University, Israel. One hundred fifty women undergoing assisted reproduction technique (ART). Intracytoplasmic sperm injection (ICSI) was performed in MI oocytes that were retrieved after ovarian stimulation. A portion of these oocytes extruded their polar body (rescued in vitro-matured metaphase II [IVM-MII]) after different incubation periods and the remainder did not (arrested MI oocytes). Fluorescence in situ hybridization was performed using probes for chromosomes X, Y, 18. Fertilization rate, number of blastomeres, and embryo euploidy. Embryos from rescued IVM-MII oocytes showed significantly higher fertilization rates and more blastomeres per embryo compared with those from arrested MI oocytes (58.5% vs. 43.9% and 5.7 vs. 5.0, respectively). The chromosomal analysis of these embryos revealed a high rate of aberrations (80.6%), mainly complex mosaics. This rate was elevated in embryos from arrested IVM oocytes (97.2%), and after longer incubation periods. No chromosomally normal embryos were found after 24 hours of incubation of their corresponding oocytes. Embryos originating from MI oocytes have a high rate of chromosomal aneuploidy, and their replacement should be reconsidered.

Pronuclear morphology differs between women more than 38 and women less than 30 years of age

Pronuclear morphology has been reported as a good tool for studying embryo development and euploidy. Comparing two groups of women with different aneuploidy risk, women more than 38 years old (n = 28) known to be at high risk of aneuploidy, and women under 30 years old (n = 35), this study investigated whether pronuclear morphology could be used routinely as an alternative to preimplantation genetic screening (PGS) in countries where PGS is prohibited. Pronuclear morphology was evaluated for 301 zygotes and related to embryo quality and pregnancy outcome. For the older women, an increased frequency of zygotes with abnormal polar body and pronuclei alignment was observed, i.e. type gamma, with 93% aneuploidy risk (26.0 versus 15.1% P < 0.05) and fewer zygotes with a good development prognosis (36.4 versus 47.8%; P < 0.05). A1alpha configuration was associated with good implantation rate and was not related to day 2 embryo quality. This configuration was less frequent in the group of women more than 38 years old and among non-pregnant women under 30 years, compared with pregnant women under 30 years old. Pronuclear morphology seemed linked to age, but not associated with embryo quality. A larger study allowing correlation analysis is necessary to confirm the value of these criteria and the link to a woman's age.

Low oxygen tension and euploidy after preimplantation genetic screening

In 2002 Bean and colleagues suggested a higher rate of mitotic non-disjunction in 5% CO2 in air. However when cultured in a 5% oxygen (O2) concentration the rate of mitotic induced mosaicism returned to the in vivo control models. The purpose of this study is to determine if the introduction of reduced O2 culture microenvironment would yield a higher rate of euploidy in preimplantation genetic screening (PGS) patients. Prospective cohort study of PGS patients where embryos were cultured in a 20% O2 and 5% O2 microenvironment. Embryos were cultured individually in a Sage sequential culture medium in 6% CO2 and air or lowered O2 (5%) balanced with nitrogen. On day 3 embryos >4 cells were subjected to biopsy of one cell in a Sage Ca/Mg free medium. The rate of blastocyst formation was evaluated in the two culture systems. Euploidy was determined from the reference laboratory report as normal or abnormal. Additionally, the rate of blastocyst formation was evaluated for euploid and aneuploid embryos. A total of 933 embryos were subjected to embryo biopsy on day 3 post insemination. Where 456 embryos were biopsied and cultured in the low (5%) O2 group and 477 embryos in the elevated (20%) O2. In the low oxygen microenvironment there was no significant (P=0.27) increase in the rate of euploidy in embryos as determined by FISH. There was a euploidy rated of 152/456 (33%) in low O2 and 143/477 (30%) in the CO2 in air culture system (not significant). In the low O2 culture system there was a significantly (P=0.004) higher rate of blastocyst formation for euploidy embryos in the low O2 as compared to elevated O2. Euploid embryos developed to blastocyst at a rate of 115/152 (76%) in low O2 vs. 86/143 (43%) in elevated O2. Where as aneuploid embryos in the low O2 vs. the elevated O2 was 141/304 (46%) and 138/334 (41%) respectively (not significant). Results show there was no decrease in mitotic non-disjunction in the human with variable oxygen tensions on the embryo. Interestingly we did show there were significantly more euploid blastocysts available for transfer when culturing in a lower O2 environment. Additionally, there was no significant increase in aneuploid embryos that developed to the blastocyst stage in low O2 vs. higher oxygen levels. Therefore showing there is an advantage to culturing embryos in low O2 in order to yield the highest number of good quality embryos available for embryo transfer.

Embryo culture to the blastocyst stage does not select for gender

Reports of increased developmental rates in male embryos have resulted in concerns that day 5 blastocyst transfer may lead to gender selection. We compared blastocyst development and prevalence of euploidy in XX vs. XY embryos. Retrospective analysis. We identified all women who underwent in vitro fertilization (IVF) with their first preimplantation genetic diagnosis (PGD) cycle for recurrent miscarriage, recurrent IVF failure, advanced maternal age, or other indications between January 1 and December 31, 2006. Fluorescence in situ hybridization was utilized to analyze 9 or 12 chromosomes. Embryos with abnormal sex chromosomes were excluded. P values were adjusted to account for lack of independence among embryos from the same woman. A total of 481 embryos from 99 cycles in 99 patients with complete results for the 9-chromosome panel were analyzed. 235 (49%) were XX and 246 (51%) were XY. The prevalence of euploidy was similar between the XX and XY embryos (30% vs. 32%, P=0.73). XX and XY embryos were equally likely to develop to the blastocyst stage by day 5 (59% vs. 60%, P=0.84), and those that became blastocysts had similar proportions of euploidy (41% vs. 37%, P=0.43). Results were similar in a subset of embryos in which all 12 chromosomes were analyzed. Abnormal numbers of individual autosomes were no more likely to occur in XX than XY embryos. XX and XY embryos are equally likely to develop to the blastocyst stage by day 5. Moreover, XX and XY blastocysts are equally likely to be euploid. There is no predilection for aneuploidy of any single autosome to occur with greater frequency in XX vs. XY embryos. Our data suggest that day 5 blastocyst culture does not result in gender selection and that euploidy and aneuploidy are not gender dependent.

The relationship between early embryo cleavage and euploidy

Non-invasive predictors of euploidy in embryos would be instrumental in reducing the number of embryos transferred as well as the rate of high order multiples. Early cleavage has been shown to improve pregnancy outcomes as well as embryos developmental potential. The objective of this study is to determine if early cleavage at 24 to 27 hours post insemination (hpi) is a predictor of euploidy in embryos. Prospective cohort study of preimplantation genetic diagnosis (PGD) embryos. All fertilized zygotes were evaluated 24 to 27 hpi. A grade of 2 cell (early cleaved), 0PN or 2PN score was recorded. Embryos were evaluated on day 3 for cell number and percent fragmentation. One cell was biopsied from day 3 embryos ≥6 cells in Ca++/Mg++ free HEPES buffered Medium. Biopsied blastomeres were fixed in a 3:1 methanol: acetic acid on a glass slide. Cells were then analyzed for up to 9 chromosomes (13, 15, 16, 17, 18, 21, 22, X, and Y). A total of 488 embryos were analyzed to determine ploidy status. Early cleavage resulted in a euploidy rate of 50 of 129 (39%). The 0PN subgroup yielded a euploidy rate of 51/175 (29%). Lastly, 2PN's produced a euploidy rate of 51/184 (28%). Early cleaved embryos yielded significantly (P=0.04) more euploid embryos compared to 2PN's. Early cleavage 24 to 27 hpi is a predictor of euploidy, thus supporting the hypothesis of this study. There was no significance between early cleavage and 0PN's. However, there is a trend that may prove significant with more data. Recent studies have shown that euploid embryos develop to blastocyst more frequently than aneuploid embryos. Combining early cleavage and blastocyst development may prove instrumental in optimizing pregnancy outcomes while reducing the number of embryos transferred.