Embryo selection by the first cleavage parameter between 25 and 27 hours after ICSI

Embryo culture and selection: morphological criteria

In this chapter, we have outlined the various morphological criteria for selection of the best embryo at each important milestone encountered in the progress from the oocyte to the blastocyst. As Gerris et al. stated, a combination of one, two, or even three selection points should lead to a more accurate selection of the best embryo, as no one criterion is better than the other. An embryo that fails to meet the entire set of selection criteria must be avoided as culture cannot correct an impaired embryo.

Eliminating the effect of pathomorphologically formed sperm on resulting gravidity using the intracytoplasmic sperm injection method

The aim of the present study was to test whether it is possible to eliminate a high percentage of morphologically abnormal sperm in male ejaculate by assisted reproduction using the intracytoplasmic sperm injection (ICSI) method. Treatment success was evaluated by comparing fertilization, clinical pregnancy and reproduction rates between males with heavy teratospermia (≤1% morphologically normal spermatozoa) and males with a higher percentage (>1%) of normal sperm. In total, 174 patients who had previously undergone 174 ICSI cycles (1 per each pair) were evaluated retrospectively. In the group of patients with heavily impaired sperm morphology (n=37), the percentage of normal spermatozoa was ≤1%. In the second group, males with >1% normal spermatozoa (n=137) were considered as patients with mildly impaired sperm morphology. The results of partner fertilization in these two groups were compared and a lower number of fertilized oocytes was identified in the patients with heavily impaired sperm morphology (P=0.038). However, neither the gravidity nor the take-home baby rates of the partners differed between the patients with mildly and heavily impaired sperm morphology. Trends opposite to that for fertilization were observed for gravidity and delivery [odds ratio (OR), 0.62; 95% confidence interval (CI), 0.29–1.30; OR, 0.55; 95% CI, 0.26–1.24, respectively]. This indicates that the lower number of fertilized oocytes was not associated with the overall outcome of fertilization and that patients with heavily impaired sperm morphology experience the same benefit from ICSI as patients with mildly impaired sperm morphology.

Accuracy of a combined score of zygote and embryo morphology for selecting the best embryos for IVF

OBJECTIVE

To evaluate the accuracy of a scoring system combining zygote and embryo morphology in predicting the outcome of in vitro fertilization (IVF) treatment.

METHODS

In a study group, 117 consecutive IVF or intracytoplasmic sperm injection (ICSI) cycles with embryo transfer were carried out and 312 embryos were scored using a combined scoring system (CSS) of zygote and embryo morphology before transplantation. In a control group, a total of 420 IVF or ICSI cycles were carried out and 1176 embryos were scored using a cumulative embryo score (CES). The effects of the combined scoring system on the embryo implantation rate and pregnancy rate per cycle were analyzed.

RESULTS

Using the combined scoring system, the embryo implantation rate (27.6%) and the clinical pregnancy rate (48.7%) were significantly higher than those in the control group (20.8% and 38.6%, respectively). Also, the implantation rate of embryos scoring>or=70 (38.5%: 82 sacs/213 embryos) was significantly higher (P<0.001) than that of embryos scoring<70 (4%: 4 sacs/99 embryos). The pregnancy rate of patients with embryos scoring>or=70 using the combined scoring system (66.7%) was significantly higher (P<0.001) than that of patients with embryos scoring>or=20 using the cumulative embryo score (59.0%).

CONCLUSION

The results suggest that selecting embryos with a high score (>or=70) using the combined scoring system could increase the implantation rate and pregnancy rate, and that using a scoring system combining assessments of human zygotes and pre-implantation embryos might predict IVF outcomes more accurately than using a cumulative embryo score.

Evaluation of day one embryo quality and IVF outcome--a comparison of two scoring systems

BACKGROUND

The aim of our retrospective study was to compare the clinical usefulness of two non-invasive embryo scoring systems based either on a simplified pronuclear morphology of the zygote or on early cleavage rate, as well as their combination, for the selection of embryos with the best implantation potential in embryo transfer (ET).

METHODS

Over a period of five years, the quality of 2708 embryos from 364 IVF cycles in women under the age of 39 years was assessed using these scoring systems in a university assisted reproduction centre. ET was always performed on day 3 of cultivation. The outcome of ETs of 702 embryos scored in the respective systems or their combination was retrospectively analyzed in terms of biochemical (bPR) and clinical pregnancy rates (cPR) and implantation rate (IR). Mann-Whitney U test and t-test for differences between relative values were used, p < 0.05 was considered statistically significant.

RESULTS

There was no difference in outcome parameters in 109 cycles where only Pattern "0" zygotes, according to our simplified pronuclear morphology classification, were transferred and 140 cycles where only "other" pattern zygotes were transferred, regardless of their cleavage rate. On the contrary, significantly greater cPR and IR (p = 0.003 and p = 0.006, respectively) were achieved in 120 cycles where only early cleavage (EC) embryos were transferred compared with 152 cycles where only non early cleavage (NEC) embryos were transferred regardless of their pronuclear morphology. The best outcome in terms of cPR (56%) and IR (43%) was found in 50 cycles when Pattern "0" and EC embryos only were used for transfer.

CONCLUSION

The results indicate that early cleavage is a better independent marker of implantation potential than zygote morphology. The best outcome can be achieved if both embryo scoring systems are used jointly and the embryo is classified as EC and Pattern "0".

Cycle outcome can be predicted by the growth profile of untransferred cleavage-stage embryos

Excess embryos obtained from intracytoplasmic sperm injection cycles may be cultured and observed until day 5 if the couple receiving treatment do not want them to be cryopreserved. In order to investigate the correlation between blastocyst formation in extended culture and pregnancy outcome, 194 patients treated in two separate IVF units were examined retrospectively. The patients were separated into two groups: group 1 with at least one blastocyst formed in culture, and group 2 with no blastocyst formation. The pregnancy rates were 60.0% and 41.7% for groups 1 and 2, respectively. The pregnancy rate in group 1 was statistically significantly higher than in group 2 (P = 0.01). The results suggest that the developmental potential of embryos obtained from a single assisted reproduction treatment cycle may be similar and that blastocyst formation in vitro may help to predict the pregnancy outcome of that cycle.

Laser-assisted hatching of cryopreserved-thawed embryos by thinning one quarter of the zona

Laser-assisted hatching is little documented in the literature regarding its efficacy in cryopreserved-thawed (CT) embryo transfer cycles. The aim of the present study was to evaluate in a randomized manner the efficacy of thinning one quarter of the zona pellucida of CT embryos to a depth of 50-80% of the original thickness, via laser treatment (the qLZT-AH procedure), in improving implantation and pregnancy rates. Two populations were studied: population I, patients who had all their supernumerary embryos cryopreserved, regardless of their morphology, and population II, patients at risk of ovarian hyperstimulation syndrome who had all their embryos cryopreserved. Artificial and natural protocols were used for the embryo transfers. A total of 350 laser-thinned CT embryos were compared with 352 intact zona embryos. No difference in implantation or pregnancy rate was found after using qLZT-AH in either population. These findings suggest that qLZT-AH should not be routinely performed in cryopreserved embryo programmes.

Impact of the assessment of early cleavage in a single embryo transfer policy

The policy of single embryo transfer (SET) adopted for women <36 years old since 1 July 2003, strongly calls for improvement of embryo selection. A total of 196 cycles in which SET was performed were randomly allocated to two groups. In the first group, early cleavage was assessed (ECA) 25 h after insemination. The embryo with the best score that cleaved early, if present, was selected for transfer. In the second group, early cleavage was not assessed (ECNA) and embryo selection was based solely on the embryo score. Ninety-eight cycles were allocated in the ECA and ECNA group respectively. Early cleavage occurred in 64% of cycles and 32.2% of embryos. Patient population and embryo morphology were similar between the two groups, and similar delivery rates were observed (27.6 versus 24.5% respectively in the ECA and ECNA groups). The assessment of early cleavage as additional parameter did not improve the delivery rate in the single embryo transfer policy.

Early pronuclear breakdown is a good indicator of embryo quality and viability

OBJECTIVE

To examine whether the timing of pronuclear breakdown can be a predictor of embryo quality and viability.

DESIGN

Retrospective comparison of the development and quality of early and late developing zygotes.

SETTING

Infertility and endocrinology unit in a university hospital.

PATIENT(S)

One thousand seven hundred eighty-two zygotes obtained in 383 consecutive IVF cycles.

INTERVENTION(S)

Culture of all fertilized embryos.

MAIN OUTCOME MEASURE(S)

Number of fertilized zygotes showing early pronuclear breakdown at 22-25 hours postinsemination, embryo quality, pregnancy rates (PR), implantation rates.

RESULT(S)

Early pronuclear breakdown embryos had a significantly higher cell number (4.4 +/- 1.2) compared with the late pronuclear breakdown embryos (3.6 +/- 1.4). When comparing the frequency of the early pronuclear breakdown embryos according to the method of fertilization, we failed to find any significant difference between the IVF (37.1%) and the intracytoplasmic sperm injection (ICSI) (41.1%) groups. The transfer of early pronuclear breakdown embryos resulted in a significantly higher clinical pregnancy rate than those with late pronuclear breakdown (48.3% vs. 27.3%). The implantation rate was higher in the early pronuclear breakdown group than in the late pronuclear breakdown group (26.5% vs. 15.1%).

CONCLUSION(S)

Early pronuclear breakdown is a strong indicator of embryo viability, and may be used as an additional criterion in the selection of embryos for transfer.

Significance of morphological attributes of the early embryo

There are many morphological transformations during development of human embryos that mainly involve phenomena that can be easily assessed in living embryos by simple non-invasive microscopical observation. A clear correlation between pronuclear morphology and the ability of the resulting embryo to continue developing and to implant has been described. There is also general agreement that a positive relationship exists between early embryo morphology and implantation rate. The parameters classically involved in embryo evaluation are: cleavage rate, blastomere symmetry, cytoplasmic appearance, extent of fragmentation and blastomere nuclear status. In this paper, morphological features that have been related to embryo developmental potential are described. Furthermore, the ability of a cumulative classification scheme developed in the laboratory to predict blastocyst formation and implantation is analysed.

Implantation failures: success of assisted hatching with quarter-laser zona thinning

Implantation failure after IVF is one of the factors associated with a reduced chance of pregnancy for some patients. Assisted hatching methodologies are designed to facilitate the embryo's escape from the zona pellucida, and this strategy has been suggested as a means of improving pregnancy rates in patients with previous implantation failure. The aim of this prospective and randomized study was to evaluate the efficacy of quarter-laser zona thinning assisted hatching (qLZT-AH) in improving the implantation of embryos in patients with previous implantation failure. A total of 150 patients with a history of previous implantation failure were treated with intracytoplasmic sperm injection, and allocated into two groups: group 1, only one previous implantation failure, and group 2, repeated implantation failures. The patients in each group were randomized at the time of embryo transfer into a control group (no qLZT-AH) or experimental group where qLZT-AH was performed. For patients with repeated implantation failures, the implantation rate in those who received laser-thinned embryos was significantly higher (P = 0.02) than in those whose embryos were not laser-thinned (10.9 and 2.6% respectively). However, this difference was not observed in patients who presented with only one previous implantation failure. The data demonstrate that qLZT-AH is an effective strategy for improving the implantation of embryos in patients with repeated implantation failures.