Embryo multinucleation at the two-cell stage is an independent predictor of intracytoplasmic sperm injection outcomes

OBJECTIVE

To determine the prognostic impact of the nuclear status at the two-cell stage on intracytoplasmic sperm injection (ICSI) outcomes.

DESIGN

Retrospective study.

SETTING

Hospital.

PATIENT(S)

Only ICSI cycles with time-lapse monitoring of transferred embryos with known implantation/delivery data from November 2012 to December 2014 were included. A total of 2,449 embryos were assessed for multinucleation rates at the two- and four-cell stage, and 608 transferred embryos were studied for ICSI outcomes.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation rate (IR) and live birth rate (LBR) according to the number of multinucleated blastomeres at the two-cell stage: none (Without-MNB^2cell), one (MNB^1/2cell), and two (MNB^2/2cell); morphokinetics of MNB^2cell embryos.

RESULT(S)

Embryos with MNB^1/2cell led to lower IR (27.7%) and LBR (22.7%) than embryos Without-MNB^2cell (33.4% and 29.8%, respectively). The MNB^2/2cell embryos led to significantly lower IR (18.3%) and LBR (13.4%) than embryos Without-MNB^2cell. This difference remained significant in multivariate analysis for implantation (odds ratio 0.57; 95% confidence interval 0.34-0.94) and birth (odds ratio 0.46; 95% confidence interval 0.26-0.80), independently of the other significant parameters (women's age, time of two-cell formation, and multinucleation at the four-cell stage). Among implanted MNB^2cell, if cleavage into four cells occurred later than 37 hours after insemination, embryos were significantly more likely to lead to birth.

CONCLUSION(S)

The presence of multinucleation at the two-cell stage and more specifically in both blastomeres had a significant negative impact on birth potential. Thus, embryo multinucleation at the two-cell stage should be used as an additional noninvasive criterion for embryo selection.

Clinical Usability of Embryo Development Using a Combined Qualitative and Quantitative Approach in a Single Vitrified-Warmed Blastocyst Transfer: Assessment of Pre-Vitrified Blastocyst Diameter and Post-Warmed Blastocyst Re-Expansion Speed

Improving the safety and efficacy of assisted reproductive technology programs has been a continuous challenge. Traditionally, morphological grading has been used for embryo selection. However, only a few studies have assessed the morphokinetic variables and morphological dynamics of blastocysts. In the present study, we aimed to perform a quantitative analysis of blastocyst diameter and re-expansion speed. This in-depth morphokinetic evaluation can correlate with currently observed pregnancy outcomes. In total, 658 single vitrified-warmed blastocyst transfer cycles were performed between October 2017 and December 2021, which were divided into four groups according to the pre-vitrified blastocyst diameter. After warming, the groups were subdivided according to the blastocyst re-expansion speed. These quantitative measurements were performed using a time-lapse system. Both diameter and speed are essential in determining the blastocyst quality, while age, day of freezing, and blastocyst quality are crucial from a clinical perspective. The application of both quantitative (diameter and speed) and qualitative (blastocyst quality scores) parameters can help evaluate the clinical usability of blastocysts. This method can prove useful for embryologists in counseling their patients and determining pregnancy patient-oriented strategies.

Correlation between morphokinetic parameters and standard morphological assessment: what can we predict from early embryo development? A time-lapse-based experiment with 2085 blastocysts

Objectives:

To evaluate the association between morphology grading and morphokinetic parameters in blastocyst stage embryos cultured in a time-lapse system.

Methods:

This retrospective cohort study included patients offered fertility treatment with autologous oocytes in our clinic between October 2017 and May 2019 using a time-lapse system. The embryos were morphologically graded according to the criteria developed by Gardner and Schoolcraft and their morphokinetic parameters were recorded.

Results:

Our results indicated that the time of pronuclei fading (tPNf), time to cleavage into two (t2), four (t4), and eight (t8) cells, and time to start of blastulation (tB) were significantly different according to the morphological quality of the blastocysts formed. In the early development stage, tPNf, t2 and t4 differed between good (AA, AB, BA, BB) and poor (CC) quality potential blastocysts. The 8-cell stage time separated embryos graded as AA blastocysts in terms of morphology from embryos graded as BB. Earlier tB correlated with higher quality embryos (AA, AB, BA).

Conclusion:

Our results showed that the first kinetic parameters (tPNf, t2, and t4) distinguished top-graded from low-graded blastocysts. Between top-graded blastocysts, t8 separated BB blastocysts from AA blastocysts. And finally, tB also told apart BB blastocysts from AA, AB, and BA blastocysts. These time-related parameters may be applied even in centers without time-lapse systems.

Environmental Stress-Induced Alterations in Embryo Developmental Morphokinetics

The association between embryo morphokinetics and its developmental competence is well documented. For instance, early cleaved embryos are more competent in developing to blastocysts, whereas the proportion of abnormally cleaved embryos that further developed to blastocysts is low. Numerous factors, such as the parental age, lifestyle, health, and smoking habits have been reported to affect the embryo morphokinetics and, consequently, its development. However, less is known about the effect of environmental stressors on embryo morphokinetics. The current review discusses the effect of the most concerning environmental stressors on embryo morphokinetics. These stresses include heat stress and human-made chemicals such as phthalates (e.g., bis-(2-ethylhexyl phthalate, dibutyl phthalate, dimethyl phthalate, and their primary metabolites), herbicides (e.g., diaminochlorotriazine, the primary metabolite of atrazine), pharmaceutical compounds (e.g., carbamazepine, nocodazole) and pro-oxidant agents (cumene hydroperoxide, Triton X-100), as well as naturally occurring toxins such as mycotoxin (e.g., aflatoxin B1 and its metabolite, and ochratoxin A). In addition, this review discusses the effect of ionizing or non-ionizing radiation and viral infections (e.g., SARS-CoV-2, papillomavirus). Finally, it points out some potential mechanisms that underlie the impairment of embryo morphokinetics, and it suggests protective compounds, mainly the supplementation of antioxidants to improve the morphokinetics, and consequently, the embryo developmental competence.