Zygote score and status 1 or 2 days after cleavage and assisted reproduction outcome

Pronuclear score improves prediction of embryo implantation success in ICSI cycles

BACKGROUND

In assisted reproduction technology embryo competence is routinely evaluated on morphological criteria but efficacy remains relatively low. Additional information could be obtained by evaluating pronuclear (PN) morphology. Up to now controversial results have been reported about the prognostic value of PN score. One of the main limitations of literature data is the use of different PN classification methods. In this regard, in 2011 the ESHRE and Alpha Scientists in Reproductive Medicine defined three PN categories to standardize zygote assessment. In this study we evaluated whether the consensus ESHRE-Alpha system for the pronuclear scoring could be an useful additional criterion to improve prediction of embryo implantation potential.

METHODS

This is a retrospective, longitudinal, observational, cohort study. We included 3004 zygotes from 555 women who underwent ICSI treatment at our Center between January 2014 and June 2019. The PN were categorized as score 1: symmetrical, 2: non-symmetrical, 3: abnormal. A subset of 110 zygotes did not cleaved. On day 2-3 1163 embryos were transferred, 232 arrested, and 9 were cryopreserved. Among the 1490 embryos cultured up to day 5-7, 516 became blastocysts: 123 were transferred on day 5 and 393 were cryopreserved. Comparisons of age, cleavage and blastocyst rate, quality of embryos, implantation success among PN score groups were evaluated by chi-square test or Kruskal-Wallis test as appropriate. Potential predictors of embryo implantation were first tested in univariable analysis using generalized estimating equations taking into account correlation between embryos originated from the same patient. Then, variables potentially associated with implantation success (P<0.05) were included in a multivariable analysis for calculating the adjusted odds ratio (OR) and 95% confidence interval (CI).

RESULTS

There was no significant difference in patients'age, cleavage and blastulation rates, and embryo morphology among the three PNscore groups. The PN score 1-embryos had a greater implantation success respect to score 2-3-ones (OR 1.83; 95% CI 1.34-2.50, P=0.0001). Consistently, the pronuclear score remained predictive of implantation in top quality embryos (OR 1.68; 95%CI 1.17-2.42, P= 0.005).

CONCLUSIONS

The consensus pronuclear score may be routinely included among criteria for embryo evaluation to increase patients' chance of becoming pregnant.

Embryo quality but not pronuclear score is associated with clinical pregnancy following IVF

PURPOSE

The association between pronuclear (PN) scoring of embryos from assisted reproductive technology (ART) and clinical pregnancy remains controversial. We hypothesized that embryos with PNs scored on the day of fertilization check offer better embryo selection on day 3 and higher CPR compared to non-PN scored embryos.

METHODS

Patients (19-46 years) undergoing IVF/ICSI cycles at Montefiore's Institute for Reproductive Medicine and Health between January 2006 and December 2009 were included in our study. We analyzed fresh day 3 cycles only with autologous oocytes and partner's fresh sperm (n = 344). A total of 1,899 embryos were included. We compared CPR from non-PN scored embryos (Group 1, n = 835) with PN scored embryos (Group 2, n = 1,064). Composite scores by patient were developed based on embryo disposition. We also assessed traditional embryo grading derived from cell number, fragmentation and cell symmetry. Data analysis included chi square and t test to determine if PN scoring was associated with improved CPR, and to compare the additional variables.

RESULTS

CPR between Group 1 and Group 2 were not different (p = 0.91). CPR was significantly associated with female age, number of mature oocytes retrieved, number of day 3 embryos and grade of embryos transferred on day 3 (p < 0.05).

CONCLUSION

PN scoring was not associated with improved CPR in day 3 embryo transfers. Mean grade of transferred embryos continues to be a well-established, independent predictor of CPR. We conclude that further refinement of embryo grading by PN scoring is not beneficial.

Pronuclear morphology evaluation for fresh in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles: a systematic review

The current systematic review was aimed to assess the effectiveness of the zygote morphology evaluation in fresh in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles. All available studies reporting on zygote morphology and clinical and/or biological outcomes were analyzed. Forty studies were included in the final analysis. Fourteen different zygote scoring systems were employed. Zygote morphology correlated significantly with embryo quality and cleavage, blastocyst stage, embryonic chromosome status, in a high proportion of the studies which assessed the specific outcome [15/25 (60%), 15/20 (75%), 7/8 (87.5%), 6/6 (100%), respectively]. On the other hand, only a reduced proportion of papers showed a statistically significant relationship between implantation, pregnancy and delivery/live-birth rates and zygote morphology score [12/23 (52.2%), 12/25 (48%), 1/4 (25%), respectively]. In conclusion, our findings demonstrate the lack of conclusive data on the clinical efficacy of the zygote morphology evaluation in fresh IVF/ICSI cycles, even if biological results showing a good relationship with embryo viability suggest a role in cycles in which the transfer/freezing is performed at day 1.

Pronuclear morphology evaluation in in vitro fertilization (IVF) / intracytoplasmic sperm injection (ICSI) cycles: a retrospective clinical review

BACKGROUND

The assessment of the embryo quality is crucial to maintain an high pregnancy rate and to reduce the risk of multiple pregnancy. The evaluation of the pronuclear and nucleolar characteristics of human zygote have been proposed as an indicator of embryo development and chromosomal complement. The aim of the current study was to assess the role of pronuclear morphology evaluation in vitro fertilization (IVF) / intracytoplasmic sperm injection (ICSI) cycles.

METHODS

Retrospective clinical analysis on 755 non-elective transfers of only one embryo (ET). Embryo assessment was performed in days 1 and 2. Clinical and biological data were recorded and analyzed according to embryo and/or pronuclear morphology.

RESULTS

Both pronuclear and embryo morphology were significantly related to clinical pregnancy and live-birth rates. No significant difference in clinical pregnancy and live-birth rates was detected when the pronuclear and embryo morphology assessments were combined. Embryo morphology and maternal age were the only independent predictors of favorable outcome by logistic regression analysis.

CONCLUSIONS

Pronuclear evaluation is effective to select the best zygotes if ET is performed at day 1, whereas it did not improve the clinical outcomes when combined with embryo morphology evaluation in day 2.

Is pronuclear scoring a really good predictor for ICSI cycles?

BACKGROUND/AIMS

Since the assessments of the morphology of oocytes, zygotes and/or embryos are of crucial importance to select the best candidate for pregnancy, many morphological evaluation tools have been proposed. Although embryo scoring, particularly cleavage and blastocyst stages, is more convincing due to successful results, zygote scoring still have a bias as different outcomes. In the current study, we designed a prospective study to test the reliability of zygote scoring by focusing on zygote evaluation techniques and its relation with embryo development and embryo selection for transfer.

METHODS

A total of 1215 mature oocytes from 139 couples were evaluated for the study.

RESULTS

There is no correlation between published zygote scoring technique and embryo development.

CONCLUSIONS

We conclude that the inconsistency of data obtained from zygote scoring might be caused by the static nature of pronuclear stage embryos and thus pronuclear scoring seems to be unreliable evaluation technique for embryo selection.

Severe teratozoospermia and its influence on pronuclear morphology, embryonic cleavage and compaction

BACKGROUND

Fertilization, cell division and embryo development depend on genomic contributions from male and female gametes. We hypothesize that teratozoospermic sperm influences early embryo development and embryo compaction.

METHODS

We conducted a retrospective analysis of embryos derived from intracytoplasmic sperm injection (ICSI) cycles. Two hundred thirty-five consecutive ICSI cycles were included in the study; all treatment was provided at the Cleveland Clinic Fertility Center. Patient cycles were divided by sperm morphology based on Kruger's strict criteria: Group A, embryos where teratozoospermic sperm (0-2% normal) were used for ICSI and Group B, embryos where dysmorphic sperm (5-13% normal) were used for ICSI. All cycles analyzed were of patients doing day 3 embryo transfers. Outcome measures assessed included pronuclear (PN) pattern, syngamy, early cleavage, cell number, rate of compaction and blastulation of embryos left in culture and not transferred on day 3.

RESULTS

A total of 1762 embryos were analyzed. PN patterns were similar in Group A and Group B embryos. No differences were noted in syngamy, cleavage, cell number or blastulation rate. Studying the development of embryos in culture after day 3 transfer revealed a difference in the timeline for compaction. By day 4, 25% of Group A embryos had compacted compared to 36% in Group B (P = 0.0007). There was no difference found between Group A and Group B embryos in regards to blastulation.

CONCLUSIONS

We did not find an association between sperm morphology and clinical outcomes. The impact of teratozoospermia may be masked in ICSI cycles where fertilization, implantation rate and clinical pregnancy rate are the primary outcome measures. However, by examining the timeline of development, we were better able to discern a potential paternal effect at critical transition points from fertilization through activation.

Analysis of pronuclear zygote configurations in 459 clinical pregnancies obtained with assisted reproductive technique procedures

BACKGROUND

Embryos selection is crucial to maintain high performance in terms of pregnancy rate, reducing the risk of multiple pregnancy during IVF. Pronuclear and nucleolar characteristics have been proposed as an indicator of embryo development and chromosomal complement in humans, providing information about embryo viability.

METHODS

To correlate the zygote-score with the maternal age and the outcome of pregnancy, we analyzed the pronuclear and nucleolar morphology, the polar body alignment and the zygote configuration in 459 clinical pregnancies obtained by IVF and ICSI in our public clinic in Reggio Emilia, Italy. We derived odds ratios (OR) and Corenfield's 95% confidence intervals (CI). Continuous variables were compared with Student's t-test; P lower than .05 was considered statistically significant.

RESULTS

We observed a significant increase of "A" pronuclear morphology configuration in 38-41 years old patients in comparison to that lower than or equal to 32 years old and a significant decrease of "B" configuration in 38-41 years old patients in comparison to that lower than or equal to 32 and in comparison to that of 33-37 years old. Related to maternal age we found no significant differences in P1 and in P2 configuration. We found no correlation between zygote-score, embryo cleavage and embryo quality.

CONCLUSIONS

Our results confirm the limited clinical significance of zygote-score suggesting that it can not be associated with maternal age, embryo cleavage and embryo quality. The evaluation of embryo quality based on morphological parameters is probably more predictive than zygote-score.

Predictive factors in in vitro fertilization (IVF): a systematic review and meta-analysis

BACKGROUND

Various models have been developed for the prediction of pregnancy after in vitro fertilization (IVF). These models differ from one another in the predictors they include. We performed a systematic review and meta-analysis to identify the most relevant predictors for success in IVF.

METHODS

We systematically searched MEDLINE and EMBASE for studies evaluating IVF/ICSI outcome. Studies were included if they reported an unconditional odds ratio (OR) or whenever one could be calculated for one or more of the following factors: age, type of infertility, indication, duration of infertility, basal FSH, number of oocytes, fertilization method, number of embryos transferred and embryo quality.

RESULTS

Fourteen studies were identified. A summary OR could be calculated for five factors. We found negative associations between pregnancy and female age [OR: 0.95, 95% confidence interval (CI): 0.94-0.96], duration of subfertility (OR: 0.99, 95% CI: 0.98-1.00) and basal FSH (OR: 0.94, 95% CI: 0.88-1.00). We found a positive association with number of oocytes (OR 1.04, 95% CI: 1.02-1.07). Better embryo quality was associated with higher pregnancy chances. No significant association was found for the type of infertility and fertilization method. A summary OR for IVF indication and number of embryos transferred could not be calculated, because studies reporting on these used different reference categories.

CONCLUSIONS

Female age, duration of subfertility, bFSH and number of oocytes, all reflecting ovarian function, are predictors of pregnancy after IVF. Better quality studies are necessary, especially studies that focus on embryo factors that are predictive of success in IVF.

Routine morphological scoring systems in assisted reproduction treatment fail to reflect age-related impairment of oocyte and embryo quality

Routine morphological scoring systems in assisted reproduction treatment are based on parameters that presumably correlate with the biological quality of gametes and embryos, including chromosome abnormalities. Maternal age is a key factor predicting pregnancy and live birth, and it is therefore of considerable interest to identify age-related indicators of oocyte and embryo quality in assisted reproduction treatment. The purpose of this study was to examine whether routine morphological scoring systems reflect age-related impact on oocyte and embryo quality among 4587 couples undergoing their first assisted reproduction treatment. This study assessed over 43,000 oocytes, 25,000 embryos and 7900 transferred embryos and analysed the associations among the following parameters: number of oocytes retrieved, oocyte quality, including maturity, fertilization rates, embryo quality, based on morphological features, and treatment outcome. Advanced chronological age was found to be associated with fewer oocytes retrieved, fewer embryos available for cryopreservation, as well as lower pregnancy, implantation, live birth rates and a higher miscarriage rate. No age-related correlation was found between fertilization rates, oocyte or embryo quality. Routinely-used morphological scoring systems, such as assessment of blastomere count, shape and fragmentation, fail to reflect age-related impact on oocyte and embryo quality.