Blastomere movement post first cell division correlates with embryonic compaction and subsequent blastocyst formation

Effects of unequal-sized pronuclei and their origin on embryo development and obstetric outcomes: a time-lapse retrospective study

RESEARCH QUESTION

Do maternal and paternal pronuclear sizes and their relative differences affect embryonic development, morphokinetics and pregnancy outcomes in human embryos?

DESIGN

A total of 2516 fertilized oocytes with two pronuclei from 1207 patients were assessed using a time-lapse culture system. The associations between the pronuclear area immediately before pronuclear breakdown and its relative ratio (PNR), and embryonic, pregnancy and perinatal outcomes, were retrospectively evaluated. Perinatal outcomes were obtained from a self-reported questionnaire. Zygotes were stratified by PNR and origin of the pronuclei; embryo development, morphokinetics and morphological alterations were compared among the zygotes.

RESULTS

Areas of maternal and paternal pronuclei were not correlated with embryonic, pregnancy and perinatal outcomes. Zygotes with a PNR lower than the median (<0.88, unequal-sized pronuclei) had impaired embryo development (expanded blastocyst; P = 0.0100). Unequal-sized pronuclei resulted in a prolonged time interval between maternal and paternal pronuclear appearance, decreased nucleolus precursor body (NPB) alignment and increased incidence of asynchronous pronuclear breakdown, asymmetric division and multinucleation (P < 0.0001-0.0230). When the paternal pronucleus was smaller than the maternal pronucleus, the decreased NPB alignment, asynchronous pronuclear breakdown and abnormal cleavage were observed more frequently, resulting in significantly decreased blastocyst formation compared with the zygotes with equal-sized pronuclei (P < 0.0001-0.0030).

CONCLUSIONS

Zygotes with unequal-sized pronuclei had impairments in preimplantation development, particularly when the paternal pronucleus was smaller than the maternal pronucleus, without any adverse effects on maternal and obstetric outcomes. In addition to the number of pronuclei, evaluating PNR and pronuclear origin would be beneficial when fertilization is verified.

Is the Human Chorionic Gonadotropin Level on Day 10 After Cleaved Embryo Transfer a Predictor of Perinatal Outcome?: A Retrospective Cohort Study

This study aimed to determine whether human chorionic gonadotropin (hCG) levels at day 10 after day 2 cleaved embryo transfer can predict pregnancy and perinatal outcomes. Patients who underwent oocyte retrieval with minimal stimulation or natural cycles and fresh or vitrified-warmed transfer of a single, day 2 cleaved embryo at our clinic between November 2018 and December 2020 were included in this study. Patients were classified into four age groups for oocyte retrieval and into ten groups based on the hCG level on day 10 after embryo transfer; pregnancy complications and delivery and neonatal outcomes were examined. Of the 5,840 cycles, 3,722 (63.7%) and 2,118 (36.3%) were fresh-cleaved and vitrified-warmed embryo transfers, respectively. The mean hCG level was 24.8 mIU/mL and the clinical pregnancy and live birth rates per transfer were 29.6% and 23.4%, respectively. Maternal age at the time of oocyte retrieval, husband's age, treatment cycle, embryo type and grade, cell number, and hCG levels were correlated with pregnancy and delivery outcomes in the univariate analysis. Conversely, only maternal age and hCG levels were correlated with the outcomes in the multivariate analysis. hCG levels on day 10 post-transfer are a useful predictor of pregnancy and delivery outcomes after cleaved embryo transfer. Live birth rates vary with maternal age, even when hCG levels are the same, but they do not vary according to the treatment cycle or type of embryo transferred. Low hCG levels may be associated with vasa previa but did not affect delivery outcomes.

Fatty acid supplementation during warming improves pregnancy outcomes after frozen blastocyst transfers: a propensity score-matched study

This study aimed to examine the viability of human blastocysts after warming with fatty acids (FAs) using an in vitro outgrowth model and to assess pregnancy outcomes after a single vitrified-warmed blastocyst transfer (SVBT). For the experimental study, we used 446 discarded vitrified human blastocysts donated for research purposes by consenting couples. The blastocysts were warmed using FA-supplemented (FA group) or non-FA-supplemented (control group) solutions. The outgrowth area was significantly larger in the FA group (P = 0.0428), despite comparable blastocyst adhesion rates between the groups. Furthermore, the incidence of outgrowth degeneration was significantly lower in the FA group than in the control group (P = 0.0158). For the clinical study, we retrospectively analyzed the treatment records of women who underwent SVBT in natural cycles between January and August 2022. Multiple covariates that affected the outcomes were used for propensity score matching as follows: 1342 patients in the FA group were matched to 2316 patients in the control group. Pregnancy outcomes were compared between the groups. The rates of implantation, clinical pregnancy, and ongoing pregnancy significantly increased in the FA group after SVBTs (P = 0.0091-0.0266). These results indicate that warming solutions supplemented with FAs improve blastocyst outgrowth and pregnancy outcomes after SVBTs.

Developmental perturbation in human embryos: Clinical and biological significance learned from time-lapse images

Background

Time-lapse technology (TLT) has gained widespread adoption worldwide. In addition to facilitating the undisturbed culture of embryos, TLT offers the unique capability of continuously monitoring embryos to detect spatiotemporal changes. Although these observed phenomena play a role in optimal embryo selection/deselection, the clinical advantages of introducing TLT remain unclear. However, manual annotation of embryo perturbation could facilitate a comprehensive assessment of developmental competence. This process requires a thorough understanding of embryo observation and the biological significance associated with developmental dogma and variation. This review elucidates the typical behavior and variation of each phenomenon, exploring their clinical significance and research perspectives.

Methods

The MEDLINE database was searched using PubMed for peer-reviewed English-language original articles concerning human embryo development.

Main findings

TLT allows the observation of consecutive changes in embryo morphology, serving as potential biomarkers for embryo assessment. In assisted reproductive technology laboratories, several phenomena have not revealed their mechanism, posing difficulties such as fertilization deficiency and morula arrest.

Conclusion

A profound understanding of the biological mechanisms and significance of each phenomenon is crucial. Further collaborative efforts between the clinical and molecular fields following translational studies are required to advance embryonic outcomes and assessment.

Maternal age affects pronuclear and chromatin dynamics, morula compaction and cell polarity, and blastulation of human embryos

STUDY QUESTION

Does maternal ageing impact early and late morphokinetic and cellular processes of human blastocyst formation?

SUMMARY ANSWER

Maternal ageing significantly affects pronuclear size and intra- and extra-nuclear dynamics during fertilization, dysregulates cell polarity during compaction, and reduces blastocoel expansion.

WHAT IS KNOWN ALREADY

In ART, advanced maternal age (AMA) affects oocyte yield, fertilization, and overall developmental competence. However, with the exception of chromosome segregation errors occurring during oocyte meiosis, the molecular and biochemical mechanisms responsible for AMA-related subfertility and reduced embryo developmental competence remain unclear. In particular, studies reporting morphokinetics and cellular alterations during the fertilization and pre-implantation period in women of AMA remain limited.

STUDY DESIGN, SIZE, DURATION

A total of 2058 fertilized oocytes were stratified by maternal age according to the Society for Assisted Reproductive Technology classification (<35, 35-37, 38-40, 41-42, and >42 years) and retrospectively analysed. AMA effects were assessed in relation to: embryo morphokinetics and morphological alterations; and the presence and distribution of cell polarity markers-Yes-associated protein (YAP) and protein kinase C-ζ (PKC-ζ)-involved in blastocyst morphogenesis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

A total of 1050 cycles from 1050 patients met the inclusion criteria and were analysed. Microinjected oocytes were assessed using a time-lapse culture system. Immature oocytes at oocyte retrieval and mature oocytes not suitable for time-lapse monitoring, owing to an excess of residual corona cells or inadequate orientation for correct observation, were not analysed. Phenomena relevant to meiotic resumption, pronuclear dynamics, cytoplasmic/cortical modifications, cleavage patterns and embryo quality were annotated and compared among groups. Furthermore, 20 human embryos donated for research by consenting couples were used for immunofluorescence.

MAIN RESULTS AND THE ROLE OF CHANCE

Static microscopic observation revealed that blastocyst formation and expansion were impaired in the 41-42 and >42-year groups (P < 0.0001). The morphological grades of the inner cell mass and trophectoderm were poorer in the >42-year group than those in the <35-year group (P = 0.0022 and P < 0.0001, respectively). Time-lapse microscopic observation revealed a reduction in nucleolus precursor body alignment in female pronuclei in the 41-42 and >42-year groups (P = 0.0010). Female pronuclear area decreased and asynchronous pronuclear breakdown increased in the >42-year group (P = 0.0027 and P < 0.0122, respectively). Developmental speed at cleavage stage, incidence of irregularity of first cleavage, type and duration of blastomere movement, and number of multinucleated cells were comparable among age groups. Delayed embryonic compaction and an increased number of extruded blastomeres were observed in the >42-year group (P = 0.0002 and P = 0.0047, respectively). Blastulation and blastocyst expansion were also delayed in the 41-42 and >42-year groups (P < 0.0001 for both). YAP positivity rate in the outer cells of morulae and embryo PKC-ζ immunoflourescence decreased in the >42-year group (P < 0.0001 for both).

LIMITATIONS, REASONS FOR CAUTION

At the cellular level, the investigation was limited to cell polarity markers. Cell components of other developmental pathways should be studied in relation to AMA.

WIDER IMPLICATIONS OF THE FINDINGS

The study indicates that maternal ageing affects the key functions of embryo morphogenesis, irrespective of the well-established influence on the fidelity of oocyte meiosis.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the participating institutions. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Association between endometrial thickness before ovulation, live birth, and placenta previa rates in clomiphene citrate-treated cycles

BACKGROUND

Although a recent study reported that the pregnancy outcomes in the first trimester were more correlated with endometrial thickness on the day of the trigger than with endometrial thickness on the day of single fresh-cleaved embryo transfer, it remains unclear whether endometrial thickness on the day of the trigger can predict live birth rate after a single fresh-cleaved embryo transfer.

OBJECTIVE

This study aimed to examine whether endometrial thickness on the trigger day is associated with live birth rates and whether modifying the single fresh-cleaved embryo transfer criteria to reflect endometrial thickness on the trigger day improved the live birth rate and reduced maternal complications in a clomiphene citrate-based minimal stimulation cycle.

STUDY DESIGN

This was a retrospective study of the outcomes of 4440 treatment cycles of women who underwent single fresh-cleaved embryo transfer on day 2 of the retrieval cycle. From November 2018 to October 2019, single fresh-cleaved embryo transfer was performed when endometrial thickness on the day of single fresh-cleaved embryo transfer was ≥8 mm (criterion A). From November 2019 to August 2020, single fresh-cleaved embryo transfer was conducted when endometrial thickness on the day of the trigger was ≥7 mm (criterion B).

RESULTS

A multivariate logistic regression analysis revealed that increased endometrial thickness on the trigger day was significantly associated with an improvement in the live birth rate after single fresh-cleaved embryo transfer (adjusted odds ratio, 1.098; 95% confidence interval, 1.021-1.179). The live birth rate was significantly higher in the criterion B group than in the criterion A group (22.9% and 19.1%, respectively; P=.0281). Although endometrial thickness on the day of single fresh-cleaved embryo transfer was sufficient, the live birth rate tended to be lower when endometrial thickness on the trigger day was <7.0 mm than when endometrial thickness on the day of the trigger was ≥7.0 mm. The risk for placenta previa was reduced in the criterion B group when compared with the criterion A group (4.3% and 0.6%, respectively; P=.0222).

CONCLUSION

This study demonstrated an association of decreased endometrial thickness on the trigger day with low birth rate and a high incidence of placenta previa. A modification of the criteria for a single fresh-cleaved embryo transfer based on endometrial thickness may improve pregnancy and maternal outcomes.

Letrozole-induced endometrial preparation improved the pregnancy outcomes after frozen blastocyst transfer compared to the natural cycle: a retrospective cohort study

Background

Letrozole treatment is considered an effective option in endometrial preparation for frozen embryo transfers in patients with ovulation disorders or irregular menstruation; however, the effectiveness of letrozole-induced endometrial preparation remains unclear in ovulatory patients. Furthermore, there is no comparative study reporting on pregnancy complications and congenital anomalies after frozen embryo transfers comparing natural and letrozole-assisted cycles. This study examined whether letrozole-induced endometrial preparation affected pregnancy outcomes, perinatal outcomes, and congenital anomalies after single vitrified-warmed blastocyst transfers (SVBTs) in ovulatory patients, as compared with the natural cycle.

Methods

This historic cohort study included only patients with unexplained infertility. Overall, 14,611 patients who underwent SVBTs between July 2015 and June 2020, comprising both natural and letrozole-assisted cycles, were included. Multiple covariates that impact outcomes were used for propensity score matching; 1,911 patients in the letrozole group were matched to 12,700 patients in the natural group, and the clinical records of 1,910 patients in each group were retrospectively analysed. Cycle characteristics, pregnancy outcomes (clinical pregnancy, ongoing pregnancy, and live birth), and incidence of pregnancy complications and congenital anomalies were statistically compared between the two groups.

Results

Multivariate logistic regression analysis showed that letrozole administration during SVBT cycles significantly improved the live birth rate (P = 0.0355). Gestational age, birth length, birth weight, and infant sex, as well as the incidence of pregnancy complications and birth defects, were statistically comparable between the two groups. Furthermore, multivariate logistic regression analysis revealed that the perinatal outcomes were not affected by letrozole-induced endometrial preparation.

Conclusions

Letrozole-induced endometrial preparation improved the live birth rate compared with the natural cycle, without adverse effects on perinatal outcomes and congenital anomalies after SVBTs. Therefore, letrozole-induced endometrial preparation might be a safe and more effective strategy, especially for patients with insufficient luteal function.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05174-0.

Human 1PN and 3PN zygotes recapitulate all morphokinetic events of normal fertilization but reveal novel developmental errors

STUDY QUESTION

Does mono- (1PN) and tri-pronuclear (3PN) fertilization recapitulate the morphokinetic changes of normal bi-pronuclear (2PN) fertilization?

SUMMARY ANSWER

Abnormal fertilization retraces the overall choreography of normal fertilization but reveals novel morphokinetic phenomena and raises scientifically and clinically relevant questions.

WHAT IS KNOWN ALREADY

ART has allowed the extracorporeal observation of early human development. Time-lapse technology (TLT) has revealed the complexity of the morphokinetic changes underpinning fertilization and the importance of this process for the genetic and cellular integrity of the embryo. Abnormal fertilization has remained neglected, despite its relevance to the physiology and pathology of early human development.

STUDY DESIGN, SIZE, DURATION

This retrospective study involved TLT observation of normally (2PN, N = 2517) and abnormally (1PN, N = 41; 3PN, N = 27) fertilized oocytes generated in ICSI cycles performed between October 2019 and December 2020. Oocyte retrieval was carried out after clomiphene citrate-based minimal ovarian stimulation. Oocytes of patients with different diagnoses of infertility were included in the analysis, while cases involving cryopreserved gametes or surgically retrieved sperm were excluded.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study included 1231 couples treated for diverse infertility causes. The fraction of male factor cases was substantial (36.1%). Microinjected oocytes were assessed by a combined TLT-culture system. Oocytes not suitable for TLT assessment, owing to an excess of residual corona cells or inadequate orientation for correct observation, were not analysed. Phenomena relevant to meiotic resumption, pronuclear dynamics, cytoplasmic/cortical modifications, cleavage patterns and embryo quality were annotated and compared between groups.

MAIN RESULTS AND THE ROLE OF CHANCE

Extrusion of the second polar body (PBII) was observed in almost all 2PN/1PN (99.9% and 100.0%, respectively) and in a vast majority of 3PN zygotes (92.1%). Rates of PBII fusion with the ooplasm were much higher in 1PN and 3PN zygotes (P < 0.0001 versus 2PN). The cytoplasmic wave was observed not only in 2PN and 3PN but also in 1PN zygotes (positivity rates of 99.8% and 100% and 82.9%, respectively; P < 0.0001). More rarely, 2PN and 1PN zygotes emitted a third polar body (PBIII). The average times of this event were comparable. The presence and position of the cytoplasmic halo were comparable among the three classes of zygotes. In the 1PN group, the single PN was maternally or paternally derived in 17 and 24 zygotes, respectively, while in the vast majority of 3PN zygotes (121/127) the supernumerary PN was of maternal origin. Average times of maternal PN appearance were comparable, while average times of paternal PN appearance were delayed in 3PN zygotes (P = 0.0127). Compared with the control group, the area of the maternal PN was larger in 1PN zygotes, but smaller in 3PN zygotes (P < 0.0001). The paternal PNs displayed the same trend (P < 0.0001), although such values were consistently smaller than maternal PNs. The area of the third PN in the 3PN group was on average more than 50% smaller than those of maternal and paternal PNs. In maternal PNs of 3PN zygotes, nucleolus precursor bodies (NPBs) aligned along the area of PN juxtaposition at a lower rate compared with the 2PN group. The rate of NPB alignment was ∼50% smaller in 1PN zygotes (P = 0.0001). In paternal PNs, the rates of NPB alignment were not statistically different among the three groups. Asynchronous PN breakdown was increased in 3PN compared with 2PN zygotes (P = 0.0026). In 1PN zygotes, a developmental delay was observed starting from the disappearance of the cytoplasmic halo, reaching 9 h at the time of the first cleavage (P < 0.0001). Higher rates of abnormal cleavage patterns and blastomere fragmentation (P < 0.0001) were observed in 1PN compared to 2N and 3PN zygotes. Cleavage progression was increasingly affected after abnormal fertilization, especially 1PN, finally resulting in blastocyst formation rates of 70.2%, 12.2% and 53.5% in 2PN, 1PN and 3PN embryos, respectively (P < 0.0001). Both maternal and paternal ages were higher in cases involving 3PN fertilization.

LIMITATIONS, REASONS FOR CAUTION

The study data were obtained from ICSI, but not standard IVF, treatments carried out in a single centre. The study findings therefore require independent verification.

WIDER IMPLICATIONS OF THE FINDINGS

This study reports the first detailed morphokinetic map of human abnormal fertilization. Collectively, this evidence prompts new scientific hypotheses and raises clinical questions relevant to the aetiology and the treatment of abnormal fertilization.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the participating institutions. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Perinatal outcomes and congenital anomalies associated with letrozole and natural cycles in single fresh cleaved embryo transfers: A single-center, 10-year cohort study

Objective

To investigate and compare the safety of letrozole and natural cycles in fresh early embryo transfers.

Design

A retrospective cohort study.

Setting

A large fertility treatment center.

Patient(s)

Women who underwent natural and letrozole cycles during fresh early embryo transfer at Kato Ladies Clinic between January 2008 and December 2017.

Intervention(s)

None.

Main Outcome measure(s)

Perinatal complications and congenital anomalies.

Result(s)

No significant differences were observed in pregnancy complications, gestational age, birth weight, small for gestational age, large for gestational age, and congenital anomalies between the the women who underwent natural and letrozole cycles.

Conclusion(s)

The perinatal outcomes and congenital anomaly rates associated with letrozole and natural cycles in fresh early embryo transfers were comparable. Therefore, our data support the safe use of letrozole in fresh early embryo transfers in assisted reproductive technology.

Maternal and obstetric outcomes are influenced by developmental stage and cryopreservation of transferred embryos after clomiphene citrate-based minimal stimulation IVF

STUDY QUESTION

Is the embryo transfer (ET) method associated with maternal and perinatal outcomes after minimal stimulation IVF using clomiphene citrate (CC)?

SUMMARY ANSWER

The incidence of pregnancy complications and adverse perinatal outcomes was influenced by the developmental stage (cleavage versus blastocyst stages) and cryopreservation (fresh versus vitrified) of the transferred embryos.

WHAT IS KNOWN ALREADY

Pregnancies resulting from IVF are associated with higher risks of adverse perinatal outcomes compared to natural conceptions; therefore, the next focus in reproductive medicine should be to assess whether these increased risks are attributable to IVF. Pregnancy complications and perinatal outcomes should be considered in addition to pregnancy outcomes when selecting the ET method, however, studies that describe the influence of transfer methods on perinatal and maternal outcomes are limited.

STUDY DESIGN, SIZE, DURATION

This study retrospectively analysed a large single-centre cohort. The clinical records of 36 827 women who underwent oocyte retrieval (during a CC-based minimal stimulation cycle) followed by their first ET at the fertility treatment centre between January 2008 and December 2017 were retrospectively analysed. The patients underwent a single fresh cleavage-stage ET (SFCT), single vitrified-warmed cleavage-stage ET (SVCT) or single vitrified-warmed blastocyst transfer (SVBT). This study only included one cycle per patient.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Oocyte retrieval was performed following CC-based minimal ovarian stimulation. The embryos were transferred 2–3 days after retrieval or vitrified at the cleavage or blastocyst stage. The vitrified embryos were then warmed and transferred within the natural cycles. Pregnancy complications and perinatal outcomes were stratified according to the transfer methods used. Multivariate logistic regression analysis was performed to evaluate the effect of ET methods on the prevalence of pregnancy complications and congenital anomalies.

MAIN RESULTS AND THE ROLE OF CHANCE

The rates of clinical pregnancy and delivery were significantly different among the groups. We analysed pregnancy complications in 7502 singleton births (SFCT, 3395 cycles; SVCT, 586 cycles; and SVBT, 3521 cycles). Multivariate logistic regression analysis revealed that the adjusted odds ratio (AOR) for hypertensive disorders in pregnancy was significantly lower in the SVBT group than in the SFCT group [AOR, 0.72; 95% CI, 0.56–0.92]. The AOR for low-lying placenta was lower in the SVBT group than in the SFCT group (AOR, 0.34; 95% CI, 0.19–0.60). The AOR for placenta previa was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.21; 95% CI, 0.07–0.58 versus AOR, 0.53; 95% CI, 0.38–0.75, respectively). A total of 7460 follow-up data on neonatal outcomes was analysed. The AOR for preterm delivery was lower in the SVBT group than in the SFCT group (AOR, 0.78; 95% CI, 0.64–0.94). The AOR for low birthweight was significantly lower after SVCT and SVBT than after SFCT (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.57; 95% CI, 0.48–0.66, respectively). The AOR for small for gestational age was lower in the SVCT and SVBT groups than in the SFCT group (AOR, 0.68; 95% CI, 0.46–0.98 versus AOR, 0.44; 95% CI, 0.36–0.55, respectively). The AOR for large for gestational age babies was higher in the SVBT group than in the SFCT group (AOR, 1.88; 95% CI, 1.62–2.18). The incidence of each congenital anomaly was similar among the groups.

LIMITATIONS, REASONS FOR CAUTION

The study data were collected through self-reported parental questionnaires on maternal and neonatal outcomes. Our findings were not compared with the incidence of pregnancy complications and congenital anomalies in natural pregnancies. Furthermore, this study was retrospective in nature; therefore, further studies are required to ascertain the generalizability of these findings to other clinics with different protocols and/or different patient demographics.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrated reassuring outcomes for SVBT (in terms of a lower incidence of pregnancy complications) compared to SFCT. Our findings provide valuable knowledge that will help improve perinatal and maternal outcomes in CC-based stimulation and inform couples of the possible benefits and risks of each type of ET method.

STUDY FUNDING/COMPETING INTEREST(S)

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Characteristics of the cytoplasmic halo during fertilisation correlate with the live birth rate after fresh cleaved embryo transfer on day 2 in minimal ovarian stimulation cycles: a retrospective observational study

BACKGROUND

Information regarding the influence of cytoplasmic events during fertilisation on the clinical outcome remains limited. The cytoplasmic halo is one of these events. A previous study that used time-lapse technology found an association of the presence and morphokinetics of the cytoplasmic halo with cleavage patterns, development to the blastocyst stage, and the ongoing pregnancy rate after blastocyst transfer. Therefore, the cytoplasmic halo may be a useful predictor of the pregnancy outcome after cleaved embryo transfer. This study evaluated the ability of the cytoplasmic halo to predict a live birth after fresh cleaved embryo transfer on day 2, and sought to identify factors potentially influencing the presence and morphokinetics of the halo.

METHODS

A total of 902 embryos cultured in the EmbryoScope+® time-lapse system and subjected to single fresh cleaved embryo transfer were retrospectively analysed. The presence and duration of a cytoplasmic halo were annotated. The initial positions of the pronuclei were also observed. The correlation between the cytoplasmic halo and live birth was evaluated and the association of the cytoplasmic halo with patient, cycle, and embryonic characteristics was determined.

RESULTS

Absence of a cytoplasmic halo was associated with a significant decrease in the likelihood of a live birth after fresh cleaved embryo transfer. Prolongation of the halo, especially the duration of central repositioning of cytoplasmic granules, had an adverse impact on the live birth rate. The characteristics of the cytoplasmic halo were not affected by the ovarian stimulation method used, female age, the serum steroid hormone level on the day of trigger, or semen quality. However, the cytoplasmic halo was significantly affected by male age, oocyte diameter, and the initial position of the male pronucleus.

CONCLUSIONS

Absence or prolongation of the cytoplasmic halo was negatively correlated with the live birth rate after fresh cleaved embryo transfer. The characteristics of the cytoplasmic halo were strongly associated with oocyte diameter, male age, and the initial position of the male pronucleus. These findings indicate that the characteristics of the cytoplasmic halo can be used to select more competent embryos for transfer at the cleavage stage.

Blastomere movement correlates with ploidy and mosaicism in early-stage human embryos after in vitro fertilization

Embryos undergo chaotic division and decrease in quality on day 3 with a reduction in the rates of subsequent blastocyst formation. Disordered cleavage causes a deterioration in embryonic quality, here we assessed the relationship between an cleavage model in first mitosis and the chromosomal status of human embryos, and discuss the potential biological and clinical implications for the cleavage model as a single parameter that can be used to assess embryonic quality. Thirty-two infertile couples, with normal karyotypes and who underwent their first IVF cycle were recruited to donate one normal two-cell-stage embryo each for this study between 2019 and 2020. Twenty-eight two-cell embryos underwent preimplantation genetic testing of each blastomere, and four chaotic-division embryos were stained with Hoechst and cultured in a confocal laser-scanning microscopy incubator system. This system showed high specificity and PPV but low sensitivity and NPV using the CM in the prediction of euploidy, indicating that CM could be considered a screening method for embryo selection; additional observational studies using the CM to select transferable embryos are needed before it can be used in clinical practice.

Comparing prediction of ongoing pregnancy and live birth outcomes in patients with advanced and younger maternal age patients using KIDScore™ day 5: a large-cohort retrospective study with single vitrified-warmed blastocyst transfer

BACKGROUND

The KIDScore™ Day 5 (KS-D5) model, version 3, is a general morphokinetic prediction model (Vitrolife, Sweden) for fetal heartbeat prediction after embryo transfer that was developed based on a large data set that included implantation results from a range of clinics with different patient populations, culture conditions and clinical practices. However, there was no study to comparing their pregnancy and live birth prediction ability among different maternal age. The aim of this study is to analyze the performance of KS-D5 in predicting pregnancy and live birth in various maternal age groups after single vitrified-warmed blastocyst transfer (SVBT).

METHODS

A total of 2486 single vitrified-warmed blastocyst transfer (SVBT) cycles were analyzed retrospectively. Confirmed fetal heartbeat positive (FHB+) and live birth (LB+) rates were stratified by Society for Assisted Reproductive Technology (SART) maternal age criteria (< 35, 35-37, 38-40, 41-42 and ≥ 43 years of age). Within each age group, the performance of the prediction model was calculated using the AUC, and the results were compared across the age groups.

RESULTS

In all age groups, the FHB+ rates decreased as the KIDScore decreased (P <  0.05). Conversely, the AUCs increased as the maternal age increased. The AUC of the < 35 age group (0.589) was significantly lower than the AUCs of the 41-42 age group (0.673) and the ≥43 age group (0.737), respectively (P <  0.05). In all age groups, the LB+ rates decreased as the KIDScore decreased (P <  0.05). Conversely, the AUCs increased as the maternal age increased. The AUC of the ≥43 age group (0.768) was significantly higher than the AUCs of other age groups (P <  0.05; < 35 age group = 0.596, 35-37 age group = 0.640, 38-40 age group = 0.646, 41-42 age group = 0.679).

CONCLUSIONS

In the present study, we determined that the KIDScore model worked well for prediction of pregnancy and live birth outcomes in advanced age patients.

Digital PCR Detection of mtDNA/gDNA Ratio in Embryo Culture Medium for Prediction of Embryo Development Potential

PURPOSE

The ratio of mitochondrial DNA to genomic DNA (mtDNA/gDNA) in embryo culture medium as a predictor of embryonic development is a new method of noninvasive embryo screening. However, current tests based on this concept have proven inconsistent. The aim of this study was to define the predictive value of the ratio of mtDNA/gDNA for embryonic developmental potential.

MATERIALS AND METHODS

We used digital PCR to measure mtDNA/gDNA ratios in day 3 culture media of 223 embryos from 56 patients. We compared the relationship between the predictive value of mtDNA/gDNA ratio and each of embryo fragmentation, embryo morphological grade, and blastocyst formation.

RESULTS

mtDNA/gDNA ratio decreased significantly with a decrease in embryo rating: 22.54 (44.66); 31.25 (36.97) and 46.33 (57.11); Grades A vs C, P = 0.006; B vs C, P = 0.015. mtDNA/gDNA ratio increased overall with an increase in embryo fragment content but did not differ significantly between high-, -medium, and poor-quality embryos. Interestingly, this trend differed from that of the unformed blastocysts. mtDNA/gDNA ratio of cleavage stage embryos forming blastocysts was lower (P=0.005). Trends of mtDNA/gDNA ratio differed according to inner cell mass (ICM) and trophectoderm (TE) levels, but not significantly. mtDNA/gDNA ratio in day 3 culture medium was not significantly improved over morphological scores.

CONCLUSION

We hereby show the correlation of mtDNA/gDNA ratio in the culture medium of developing embryos. The correlation between the mtDNA/gDNA ratio and early embryonic development was controversial. Furthermore, an increase in mtDNA/gDNA ratio might indicate reduced development potential, but the difference remains insufficient for application as a clinical predictor.

Embryo Morphokinetics and Blastocyst Development After GnRH Agonist versus hCG Triggering in Normo-ovulatory Women: a Secondary Analysis of a Multicenter Randomized Controlled Trial

Gonadotropin-releasing hormone agonist (GnRHa) for final oocyte maturation, along with vitrification of all usable embryos followed by transfer in a subsequent frozen-thawed cycle, is the most effective strategy to avoid ovarian hyperstimulation syndrome (OHSS). However, less is known about the ovulation induction triggers effect on early embryo development and blastocyst formation. This study is a secondary analysis of a multicenter, randomized controlled trial, with the aim to compare embryo development in normo-ovulatory women, randomized to GnRHa or human chorionic gonadotropin (hCG) trigger. In all, 4056 retrieved oocytes were observed, 1998 from the GnRHa group (216 women) and 2058 from the hCG group (218 women). A number of retrieved oocytes, mature and fertilized oocytes, and high-quality embryos and blastocysts were similar between the groups. A sub-analysis in 250 women enrolled at the main trial site including 2073 oocytes was conducted to compare embryo morphokinetics and cleavage patterns with EmbryoScope time-lapse system. In total, 1013 oocytes were retrieved from the GnRHa group (124 women) and 1060 oocytes were retrieved from the hCG group (126 women). Morphokinetic parameters and cleavage patterns were comparable between the groups. However, embryos derived from the GnRHa group were less likely to perform rolling during their development than the embryos from the hCG trigger group (OR = 0.41 (95%CI 0.25; 0.67), p-value 0.0003). The comparable results on embryo development and utilization rates between the GnRHa and hCG triggers is of clinical relevance to professionals and infertile patients, when GnRHa trigger and freeze-all is performed to avoid OHSS development. ClinicalTrials.gov Identifier: NCT02746562.

The optimal number of embryo cells for effective pregnancy and decrease of multiple pregnancy rate in frozen-thawed embryo transfer

To investigate the effect of the number of embryo cells on the clinical outcome of frozen-thawed embryo transfer and explore the optimal policy for decreases of multiple pregnancy rate, patients who experienced day 3 vitrified double frozen-thawed embryo transfer were retrospectively analyzed. According to the number of embryonic cells in each pre-frozen embryo, the patients were divided into six groups: 8C₂ (two 8-cell embryos), 8C₁- < 8C₁ (one 8-cell embryo and one under-8-cell embryo), 8C₁- > 8C₁ (one 8-cell embryo and one over-8-cell embryo), < 8C₂ (two under-8-cell embryos), < 8C₁- > 8C₁ (one under-8-cell embryo and one over-8-cell embryo), and > 8C₂ (two over-8-cell embryos). The clinical data were analyzed. The classification decision tree was used to analyze the optimal transfer strategy. A total of 2184 cycles of day 3 vitrified double frozen-thawed embryo transfer were enrolled. In day 3 double frozen-thawed embryo cycles, the 8C₂ group and 8C₁- > 8C₁ group had significantly (P < 0.05) higher pregnancy and multiple pregnancy rates than the other groups. No significant (P > 0.05) difference existed in the pregnancy rate and live birth rate between the 8C₁- < 8C₁ group, 8C₂ group and 8C₁- > 8C₁ group, but the implantation rate and multiple pregnancy rate in the 8C₁- < 8C₁ group were significantly (P < 0.05) lower than in the other two groups. Compared with the multiple pregnancy rate of all cycles, the cycles in two branches showed significantly (P < 0.05) higher multiple pregnancy rates (≤ 29 years old: 8C₂ / 8C₁- > 8C₁; 29 < age ≤ 36 years for the first transfer: 8C₂ / 8C₁- < 8C₁ / 8C₁- > 8C₁, one branch showed similar rate (≤ 29 years old: 8C₂ / 8C₁- > 8C₁) for the first transfer, and the remaining four branches demonstrated significantly (P < 0.05) lower rates. The clinical pregnancy rates before and after optimization were 51.0% vs 50.5%, and the multiple pregnancy rates were 38.5% vs 16.9%. In conclusion, the number of pre-frozen embryonic cells is an important factor affecting the clinical outcome of frozen-thawed embryo transfer in day 3 double good embryos frozen-thawed cycles. The age of patient, number of embryo cells, and the first time of transfer are the most valuable parameters for prediction. For women ≤ 29 years old, the single embryo transfer (SET) strategy was to choose an embryo ≥ 8 cells, and for women with < 29 age ≤ 36 years old, the SET strategy in the first transfer was to choose an embryo ≥ 8 cells.

Prolactin receptor expression and its role in trophoblast outgrowth in human embryos

RESEARCH QUESTION

What is the gene expression pattern of prolactin receptor (PRLR) in human pre-implantation embryos and what are its functions during the embryonic development and adhesion process?

DESIGN

A total of 405 discarded human vitrified oocytes and embryos donated for research by consenting couples were used in this study. The oocytes and embryos were used to analyse PRLR expression and to evaluate the influence of prolactin (PRL) supplementation in the embryo culture medium on embryo developmental competence and viability. The rates of blastocyst development and adhesion, outgrowth area, cytoskeletal reorganization and nascent adhesion formation were compared between groups.

RESULTS

PRLR expression increased significantly after embryo compaction (P < 0.0001) and blastulation (P < 0.0001). Supplementation of the embryo culture medium with PRL did not improve the developmental rate and morphological grade. In contrast, blastocyst outgrowth was significantly increased in embryos cultured with PRL (P = 0.0004). Phosphorylation of JAK2, downstream of the prolactin receptor family, was markedly higher in the PRL-treated embryos than in embryos cultured without PRL. Furthermore, the expression of mRNAs encoding ezrin-radixin-moesin proteins and epithelial-mesenchymal transition-related genes was stimulated by the activation of PRL-JAK2 signalling. The PRL-treated embryos had higher mRNA expression of integrins than non-treated embryos, and transcriptional repression of cadherin 1 was observed after PRL treatment. More nascent adherent cells expressed focal adhesion kinase and paxillin in PRL-treated embryos than in non-treated embryos.

CONCLUSIONS

Human embryos express PRLR at the morula and blastocyst stages, and PRLR signalling stimulates blastocyst adhesion by promoting integrin-based focal adhesions and cytoskeletal organization during trophoblast outgrowth.

Anti-Müllerian hormone is correlated with cumulative live birth in minimal ovarian stimulation with clomiphene citrate: a retrospective cohort study

BACKGROUND

Several studies have investigated the correlation between the serum anti-Müllerian hormone (AMH) level and in vitro fertilization (IVF) outcomes in controlled ovarian stimulation cycles; however, studies regarding the correlation of the serum AMH level with IVF outcomes in minimal ovarian stimulation cycles remain limited. In this study, we aimed to analyze the correlation of the serum AMH level with ovarian responsiveness, embryonic outcomes, and cumulative live birth rates in clomiphene citrate (CC)-based minimal ovarian stimulation cycles.

METHODS

Clinical records of 689 women whose entire ovarian stimulation regimen consisted solely of minimal stimulation cycle IVF using CC alone from November 2017 to October 2019 were retrospectively reviewed. The association between IVF outcomes and the serum AMH level before the initiation of the first fertility treatment was analyzed. Furthermore, the correlation of the serum AMH level with cumulative live birth rates after IVF treatment was assessed. The Cochran-Armitage test, Pearson's chi-squared test, Spearman rank correlation test, Student's t-test, one-way analysis of variance, logistic regression analysis, Kaplan-Meier method and Cox proportional hazards model were used to analyze the data.

RESULTS

The serum AMH level positively correlated with the number of retrieved oocytes, blastocyst formation rate, blastocyst cryopreservation rate, and live birth rate per oocyte retrieval in CC-based minimal ovarian stimulation cycles without any exogenous gonadotropin administration. Furthermore, the cumulative live birth rate and treatment period required for conceiving were strongly associated with the serum AMH level at the initiation of fertility treatment.

CONCLUSIONS

A low serum AMH level correlated with low ovarian responsiveness, impaired pre-implantation embryonic development, and decreased cumulative live birth rate in CC-based minimal ovarian stimulation cycles. Therefore, the cycle success rate would be predicted by measuring the serum AMH level in minimal ovarian stimulation with CC alone.

Effects of gonadotropin administration on clinical outcomes in clomiphene citrate-based minimal stimulation cycle IVF

PURPOSE

Exogenous gonadotropins (EGn) have been used occasionally in clomiphene citrate (CC)-based minimal stimulation cycles to compensate insufficient secretion of endogenous gonadotropin; however, the effectiveness of EGn supplementation remains unknown. In the present study, we assessed whether EGn improved pregnancy outcomes in CC-based minimal stimulation cycles.

METHODS

A total of 223 patients treated with CC and EGn (CC-EGn group) were matched one to one to patients treated with CC only (CC group) by propensity score matching. Embryonic and pregnancy outcomes were retrospectively compared between the groups.

RESULTS

The numbers of retrieved oocytes, fertilized oocytes, cleaved embryos, and cryopreserved blastocysts were increased in the CC-EGn group compared with the CC group. However, the cumulative live birthrate was comparable between the two groups. Although the increased number of retrieved oocytes was correlated significantly with improvement of the cumulative live birthrate in both groups, the correlation tended to be lower in the CC-EGn group than in the CC group (odds ratio, 1.193 vs 1.553).

CONCLUSIONS

In CC-based minimal stimulation cycles, the stimulation should be started with CC only, and EGn administration should be scheduled only if insufficient secretion of endogenous gonadotropin is observed in the late follicular phase.