Blastocyst Vitrification and Trophectoderm Biopsy Cumulatively Alter Embryonic Gene Expression in a Mouse Model

Current understanding of the pathogenesis of placenta accreta spectrum disorder with focus on mitochondrial function

AIM

The refinement of assisted reproductive technology, including the development of cryopreservation techniques (vitrification) and ovarian stimulation protocols, makes frozen embryo transfer (FET) an alternative to fresh ET and has contributed to the success of assisted reproductive technology. Compared with fresh ET cycles, FET cycles were associated with better in vitro fertilization outcomes; however, the occurrence of pregnancy-induced hypertension, preeclampsia, and placenta accreta spectrum (PAS) was higher in FET cycles. PAS has been increasing steadily in incidence as a life-threatening condition along with cesarean rates worldwide. In this review, we summarize the current understanding of the pathogenesis of PAS and discuss future research directions.

METHODS

A literature search was performed in the PubMed and Google Scholar databases.

RESULTS

Risk factors associated with PAS incidence include a primary defect of the decidua basalis or scar dehiscence, aberrant vascular remodeling, and abnormally invasive trophoblasts, or a combination thereof. Freezing, thawing, and hormone replacement manipulations have been shown to affect multiple cellular pathways, including cell proliferation, invasion, epithelial-to-mesenchymal transition (EMT), and mitochondrial function. Molecules involved in abnormal migration and EMT of extravillous trophoblast cells are beginning to be identified in PAS placentas. Many of these molecules were also found to be involved in mitochondrial biogenesis and dynamics.

CONCLUSION

The etiology of PAS may be a multifactorial genesis with intrinsic predisposition (e.g., placental abnormalities) and certain environmental factors (e.g., defective decidua) as triggers for its development. A distinctive feature of this review is its focus on the potential factors linking mitochondrial function to PAS development.

Metabolic Profiles of Offspring Born From Biopsied Embryos from Toddlerhood to Preschool Age

CONTEXT

Embryo biopsy, which is necessary for preimplantation genetic testing (PGT), has not been fully investigated regarding its potential influences and safety. Previous studies of children born from biopsied embryos (PGT children) have primarily centered around their growth and neuropsychological development, while there remains limited knowledge concerning their endocrine and metabolic parameters.

OBJECTIVE

This study aims to examine the effect of trophectoderm (TE) biopsy on metabolic outcomes for PGT children.

METHODS

A total of 1267 children from the Center for Reproductive Medicine, Shandong University, who were conceived through in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) with and without PGT, were analyzed in this study. Three sets of measurements pertaining to growth and metabolism were taken at each predetermined follow-up time point. The linear regression models within a generalized estimating equation were employed to examine the associations between the PGT and each outcome measure and the approach of false discovery rate was used to correct for multiple comparisons.

RESULTS

After controlling for confounding factors and correcting for multiple comparisons, no statistically significant difference was identified in any of the measured variables between the PGT children and children conceived by IVF alone (IVF children) and children conceived through IVF using ICSI (ICSI children). The same is true also for age- or sex-based subgroup analyses.

CONCLUSION

Between the ages of 1 and 5 years, there are no clinically adverse metabolic outcomes observed in PGT children, and their metabolic profiles are essentially identical to those of IVF children and ICSI children.

Association between the length of in vitro embryo culture, mode of ART, and the initial endogenous hCG rise in ongoing singleton pregnancies

STUDY QUESTION

Is there an association between the length of in vitro culture, mode of ART and the initial endogenous hCG rise, in cycles with a foetal heartbeat after single embryo transfer (ET) and implantation?

SUMMARY ANSWER

Both the length of in vitro culture and the mode of ART have an impact on the initial endogenous rise in hCG in singleton pregnancies.

WHAT IS KNOWN ALREADY

Different factors have been identified to alter the kinetics of hCG in pregnancies. Current studies show conflicting results regarding the kinetics of hCG after different types of ART (fresh vs frozen ET (FET)), the inclusion or not of preimplantation genetic testing (PGT), and the length of time in in vitro culture.

STUDY DESIGN, SIZE, DURATION

This was a multicentre cohort study, using prospectively collected data derived from 4938 women (5524 treatment cycles) undergoing IUI (cycles, n = 608) or ART (cycles, n = 4916) treatments, resulting a in singleton ongoing pregnancy verified by first-trimester ultrasound scan. Data were collected from the Danish Medical Data Centre, used by the three participating Danish public fertility clinics at Copenhagen University hospitals: Herlev Hospital, Hvidovre Hospital, and Rigshospitalet, from January 2014 to December 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The fresh ET cycles included cleavage-stage (2 or 3 days in vitro) and blastocyst (5 days in vitro) transfers. FET cycles included cleavage-stage (3 days in vitro before cryopreservation) or blastocyst (5 or 6 days in vitro before cryopreservation) transfers. The IUI cycles represented no time in vitro. To attain a comparable interval for serum-hCG (s-hCG), the ovulation induction time was identical: 35-37 h before oocyte retrieval or IUI. The conception day was considered as: the insemination day for pregnancies conceived after IUI, the oocyte retrieval day for fresh ET, or the transfer day minus 3 or 5 as appropriate for FET of Day 3 or 5 embryos. Multiple linear regression analysis was used, including days post-conception for the hCG measurement as a covariate, and was adjusted for the women's age, the cause of infertility, and the centre. For FET, a sensitivity analysis was used to adjust for endometrial preparation.

MAIN RESULTS AND THE ROLE OF CHANCE

The study totally includes 5524 cycles: 2395 FET cycles, 2521 fresh ET cycles, and 608 IUI cycles. Regarding the length of in vitro culture, with IUI as reference (for no time in in vitro culture), we found a significantly lower s-hCG in pregnancies achieved after fresh ET (cleavage-stage ET or blastocyst transfer). S-hCG was 18% (95% CI: 13-23%, P < 0.001) lower after fresh cleavage-stage ET, and 23% (95% CI: 18-28%, P < 0.001) lower after fresh blastocyst transfer compared to IUI. In FET cycles, s-hCG was significantly higher after blastocyst transfers compared to cleavage-stage FET, respectively, 26% (95% CI: 13-40%, P < 0.001) higher when cryopreserved on in vitro Day 5, and 14% (95% CI: 2-26%, P = 0.02) higher when cryopreserved on in vitro Day 6 as compared to Day 3. Regarding the ART treatment type, s-hCG after FET blastocyst transfer (Day 5 blastocysts) cycles was significantly higher, 33% (95% CI: 27-45%, P < 0.001), compared to fresh ET (Day 5 blastocyst), while there was no difference between cleavage-stage FET (Days 2 + 3) and fresh ET (Days 2 + 3). S-hCG was 12% (95% CI: 4-19%, 0.005) lower in PGT FET (Day 5 blastocysts) cycles as compared to FET cycles without PGT (Day 5 blastocysts).

LIMITATIONS, REASONS FOR CAUTION

The retrospective design is a limitation which introduces the risk of possible bias and confounders such as embryo score, parity, and ovarian stimulation.

WIDER IMPLICATIONS OF THE FINDINGS

This study elucidates how practices in medically assisted reproduction treatment are associated with the hCG kinetics, underlining a potential impact of in vitro culture length and mode of ART on the very early embryo development and implantation. The study provides clinicians knowledge that the type of ART used may be relevant to take into account when evaluating s-hCG for the prognosis of the pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

No funding was received for this study. AP has received consulting fees, research grants, or honoraria from the following companies: Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos, Merck A/S, and Organon. AZ has received grants and honoraria from Gedeon Richter. NLF has received grants from Gedeon Richter, Merck A/S, and Cryos. MLG has received honoraria fees or research grants from Gedeon Richter, Merck A/S, and Cooper Surgical. CB has received honoraria from Merck A/S. MB has received research grants and honoraria from IBSA. MPR, KM, and PVS all report no conflicts of interest.

TRIAL REGISTRATION NUMBER

The study was registered and approved by the Danish Protection Agency, Capital Region, Denmark (Journal-nr.: 21019857). No approval was required from the regional ethics committee according to Danish law.

Does embryo biopsy, independent of vitrification, impact perinatal outcomes? An analysis of perinatal outcomes following preimplantation genetic testing biopsy in fresh and frozen embryo transfer cycles

Objective

To compare neonatal outcomes in pregnancies resulting from embryos that have undergone preimplantation genetic testing (PGT) biopsy compared with no biopsy in both fresh and frozen embryo transfers (ETs) and determine whether findings are mediated by multiple births.

Design

Retrospective cohort study.

Setting

Society of Assisted Reproductive Technologies-Clinical Outcomes Reporting System data, 2014-2015.

Patients

Autologous in vitro fertilization treatment cycles using fresh or frozen blastocyst ET, with or without PGT biopsy.

Interventions

Not applicable.

Main Outcome Measures

Large for gestational age (LGA), small for gestational age, and preterm delivery. Secondary outcomes included high birthweight, low birthweight, and clinical pregnancy measures. Outcomes were evaluated using log-binomial regression models with repeated measures. Models were used to estimate the controlled direct effects of biopsy on birth outcomes that were not mediated by multiple gestations.

Results

In fresh ET, biopsy was associated with an increase in LGA (relative risk [RR] 1.45, confidence interval [CI] 1.04-2.02) that persisted in the model mediated for multiple gestation (RR 1.36, 95% CI 1.01-1.83) but was not present in an analysis restricted to elective single ET (RR 0.99, 95% CI 0.91-1.09). In frozen ET, there were no differences in any of the primary outcomes after accounting for multiple gestations.

Conclusions

In a large multicenter database, there were no differences in neonatal outcomes after PGT biopsy in frozen ET cycles, and an increase in LGA was noted in fresh transfers that persisted even after accounting for multiple gestations but was not present in analysis restricted to elective single ET.

Frozen autologous and donor oocytes are associated with differences in clinical and neonatal outcomes compared with fresh oocytes: a Society for Assisted Reproductive Technology Clinic Outcome Reporting System Analysis

Objective

To study the clinical and neonatal outcomes of embryos derived from frozen oocytes relative to fresh oocytes in both autologous and donor oocyte cycles after fresh embryo transfer (ET).

Design

This is a retrospective cohort study using the Society for Assisted Reproductive Technology Clinic Outcome Reporting System database between 2014 and 2015.

Setting

The Society for Assisted Reproductive Technology Clinic Outcome Reporting System database was used to identify autologous and donor oocyte cycles that resulted in a fresh ET during 2014 and 2015.

Patients

There were 154,706 total cycles identified that used embryos derived from fresh or frozen oocytes and resulted in a fresh ET, including 139,734 autologous oocyte cycles and 14,972 donor oocyte cycles.

Interventions

Generalized linear regression models were used to compare the clinical and neonatal outcomes of frozen oocytes relative to fresh oocytes. Models were adjusted for maternal age, body mass index, smoking status, parity, infertility diagnosis, number of embryos transferred, and preimplantation genetic testing. An additional sensitivity analysis was performed to examine singleton pregnancies separately.

Main Outcome Measures

The live birth (LB) rate was the primary outcome. Secondary outcomes include pregnancy and birthweight outcomes.

Results

Differences in clinical and neonatal outcomes between fresh and frozen-thawed oocytes after fresh ET were observed. Specifically, our study found a higher incidence of high-birthweight infants after the use of frozen oocytes relative to fresh oocytes in both autologous oocytes (12.5% [frozen] vs. 4.5% [fresh], adjusted risk ratio [aRR] 2.67, 95% confidence interval [CI] 1.65-4.3) and donor oocyte cycles (6.2% [frozen] vs. 4.6% [fresh], aRR 1.42, 95% CI 1.1-1.83). This finding remained true when the analysis was restricted to singleton gestations only for both groups: autologous (17.3% [frozen] vs. 7.1% [fresh], aRR 2.77, 95% CI 1.74-4.42) and donor oocytes (9.4% [frozen] vs. 7.8% [fresh], aRR 1.38, 95% CI 1.07-1.77). Additionally, we observed a decrease in LB (aRR 0.81, 95% CI 0.77-0.85); clinical pregnancy (aRR 0.83, 95% CI 0.8-0.87); and an increase in biochemical pregnancy loss (aRR 1.22, 95% CI 1.05-1.43) after the use of frozen oocytes in donors, but not autologous cycles.

Conclusions

Our findings of an increased incidence of high-birthweight infants after the transfer of embryos derived from frozen oocytes in both autologous and donor oocyte cycles raise questions about oocyte vitrification and deserve further study. Additionally, the finding of a decreased likelihood of LB with frozen-donor oocytes compared with fresh donor oocytes is an important finding, especially because more patients are seeking to use frozen oocytes in their donor egg cycles. Future research should be directed toward these findings to optimize the use of frozen oocytes in clinical practice.

The adverse effects of vitrification on mouse embryo development and metabolic phenotype in offspring

Embryo vitrification is a standard procedure in assisted reproductive technology. Previous studies have shown that frozen embryo transfer is associated with an elevated risk of adverse maternal and neonatal outcomes. This study aimed to explore the effects of mouse blastocyst vitrification on the phenotype of vitrified-warmed blastocysts, their intrauterine and postnatal development, and the long-term metabolic health of the derived offspring. The vitrified-warmed blastocysts (IVF + VT group) exhibited reduced mitochondrial activity, increased apoptotic levels, and decreased cell numbers when compared to the fresh blastocysts (IVF group). Implantation rates, live pup rates, and crown-rump length at E18.5 were not different between the two groups. However, there was a significant decrease in fetal weight and fetal/placental weight ratio in the IVF + VT group. Furthermore, the offspring of the IVF + VT group at an age of 36 weeks had reduced whole energy consumption, impaired glucose and lipid metabolism when compared with the IVF group. Notably, RNA-seq results unveiled disturbed hepatic gene expression in the offspring from vitrified-warmed blastocysts. This study revealed the short-term negative impacts of vitrification on embryo and fetal development and the long-term influence on glucose and lipid metabolism that persist from the prenatal stage into adulthood in mice.

Increased Risk of Preeclampsia with Assisted Reproductive Technologies

PURPOSE OF REVIEW

We summarized recent available data to assess the association between assisted reproductive technology (ART) and risk for preeclampsia.

RECENT FINDINGS

The majority of clinical studies supporting the association of preeclampsia and ART are retrospective. Published data from both clinical and pre-clinical studies suggest specific ART procedures may contribute to the increased risk, including in vitro embryo handling and development, hormone stimulation, transfer cycle types, and use of donor oocytes/embryos. Potential mechanisms include epigenetic aberrations leading to abnormal placentation, absence of factors secreted by the corpus luteum, and immunologic responses to allogenic gametes. There is an increased risk of preeclampsia following ART. Treatment plans that favor reduced preeclampsia risk should be considered for ART pregnancies. To make ART pregnancies safer, additional clinical and animal model studies are needed to elucidate the underpinnings of this risk association.

Trophectoderm biopsy is associated with adverse obstetric outcomes rather than neonatal outcomes

BACKGROUND

With the wide application of preimplantation genetic testing (PGT) with trophectoderm (TE) biopsy, the safety of PGT has always been a concern. Since TE subsequently forms the placenta, it is speculated that the removal of these cells was associated with adverse obstetrical or neonatal outcomes after single frozen-thawed blastocyst transfer (FBT). Previous studies report contradictory findings with respect to TE biopsy and obstetric and neonatal outcomes.

METHODS

We conducted a retrospective cohort study including 720 patients with singleton pregnancies from single FBT cycles who delivered at the same university-affiliated hospital between January 2019 and March 2022. The cohorts were divided into two groups: the PGT group (blastocysts with TE biopsy, n = 223) and the control group (blastocysts without biopsy, n = 497). The PGT group was matched with the control group by propensity score matching (PSM) analysis at a ratio of 1:2. The enrolled sample sizes in the two groups were 215 and 385, respectively.

RESULTS

Patient demographic characteristics were comparable between the groups after PSM except for the proportion of recurrent pregnancy loss, which was significantly higher in the PGT cohort (31.2 vs. 4.2%, P < 0.001). Patients in the PGT group had significantly higher rates of gestational hypertension (6.0 vs. 2.6%, adjusted odds ratio (aOR) 2.91, 95% confidence interval (CI) 1.18-7.18, P = 0.020) and abnormal umbilical cord (13.0 vs. 7.8%, aOR 1.94, 95% CI 1.08-3.48, P = 0.026). However, the occurrence of premature rupture of membranes (PROM) (12.1 vs. 19.7%, aOR 0.59, 95% CI 0.35-0.99, P = 0.047) was significantly lower in biopsied blastocysts than in unbiopsied embryos. There were no significant differences in regard to other obstetric and neonatal outcomes between the two groups.

CONCLUSIONS

Trophectoderm biopsy is a safe approach, as the neonatal outcomes from biopsied and unbiopsied embryos were comparable. Furthermore, PGT is associated with higher risks of gestational hypertension and abnormal umbilical cord but may have a protective effect on PROM.

A propensity score-based, comparative study assessing humid and dry time-lapse incubation, with single-step medium, on embryo development and clinical outcomes

STUDY QUESTION

Does culture in a high relative humidity atmosphere improve clinical outcomes when using a time-lapse integrated incubator and single-step culture medium?

SUMMARY ANSWER

Using an integrated time-lapse system and single-step culture medium, culture in a high relative humidity atmosphere increases the likelihood of embryos, especially those subjected to preimplantation genetic testing for aneuploidies, to achieve a pregnancy compared to those cultured in dry conditions.

WHAT IS KNOWN ALREADY

The use of a humid atmosphere inside incubators can reduce changes in culture media osmolality, which has been reported to have a significant effect on embryo quality and morphokinetics. Studies assessing the effect of humid culture (HC) in clinical outcomes are, however, scarce and inconclusive, mostly due to a high variability in culture conditions and reduced sample size.

STUDY DESIGN, SIZE, DURATION

Retrospective cohort study performed over 1627 ICSI cycles performed during 3 consecutive years in which embryo cohorts were cultured in a time-lapse incubator with three dry and three humidified chambers, and using single-step culture medium. Clinical outcomes were compared between treatments in which embryo cohorts were cultured in either humid (n = 833) or dry (n = 794) conditions.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study includes autologous treatments, with (N = 492) and without (N = 372) preimplantation genetic testing for aneuploidies (PGT-A) and ovum donation treatments (N = 763), performed in three university-affiliated private IVF centres. Stimulation, oocyte pickup and fertilization were performed according to the standard procedures of the clinic. All embryo cohorts were cultured in the same model of time-lapse incubator, distributed to either a dry or humidified chamber, while the rest of the culture variables remained equal. The population was weighted by the inverse probability of treatment to control for all measured confounders. The association between HC and the main outcome was assessed by logistic regression over the weighted population. The E-value was reported as a way of considering for unmeasured confounders. Differences in embryo development and other secondary outcomes between the study groups were assessed by Pearson Chi-squared test, ANOVA test and Kaplan-Meier survival analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

An univariable logistic regression analysis, weighted by the inverse probability of treatment, determined that embryos cultured in humid conditions are more likely to achieve a clinical pregnancy than those cultured in dry conditions (odds ratio (OR) = 1.236 (95% CI 1.009-1.515), P = 0.041, E = 1.460). Through stratification, it was determined that said effect is dependent on the type of treatment: no improvement in clinical pregnancy was present in ovum donation or autologous treatments, but a statistically significant positive effect was present in treatments with preimplantation genetic testing (OR = 1.699 (95% CI 1.084-2.663), P = 0.021, E = 1.930). Said increase does not relate with an improvement in later outcomes. Differences were also found in variables related to embryo developmental morphokinetics.

LIMITATIONS, REASONS FOR CAUTION

The retrospective nature of the study makes it susceptible to some bias linked to the characteristics of the treatments. To lessen the effect of possible biases, cases were weighted by the inverse probability of treatment prior to the evaluation of the outcome, as means to assess for measured confounders. In addition, the E-value of the weighted OR was calculated as a sensitivity analysis for unmeasured confounders. A randomized prospective study could be performed for further assessing the effect of humid conditions in clinical outcome.

WIDER IMPLICATIONS OF THE FINDINGS

These results support that embryo culture under conditions of high relative humidity contributes to optimize clinical results in undisturbed culture in a time-lapse incubator with single-step medium. To our knowledge, this is the largest study on the matter and the first performing a propensity score-based analysis.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the ''Centro para el Desarrollo Tecnologico Industrial'' from the Spanish Ministry of Science, Innovation, and Universities (CDTI-20170310) and Generalitat Valenciana and European Social Fund (ACIF/2019/264). None of the authors have any competing interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Perinatal outcomes of singleton live births after preimplantation genetic testing during single frozen-thawed blastocyst transfer cycles: a propensity score-matched study

OBJECTIVE

To determine whether singleton pregnancy achieved after preimplantation genetic testing (PGT) is associated with a higher risk of adverse perinatal outcomes than in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) singleton pregnancy.

DESIGN

A retrospective cohort study.

SETTING

A university-affiliated fertility center.

PATIENT(S)

This cohort study included singleton live births resulting from PGT (n = 232) and IVF/ICSI singleton pregnancies (n = 2,829) with single frozen-thawed blastocyst transfer. Multiple baseline covariates were used for propensity score matching, yielding 214 PGT singleton pregnancies matched to 617 IVF/ICSI singleton pregnancies.

INTERVENTION(S)

Trophectoderm biopsy.

MAIN OUTCOME MEASURE(S)

The primary outcome was gestational hypertension, and various clinical perinatal secondary outcomes related to maternal and neonatal health were measured.

RESULT(S)

Compared with IVF/ICSI singleton pregnancy, PGT singleton pregnancy was associated with a significantly higher risk of gestational hypertension (adjusted odds ratio, 2.58; 95% confidence interval, 1.32, 5.05). In the matched sample, the risk of gestational hypertension remained higher with PGT singleton pregnancy (odds ratio, 2.33; 95% confidence interval, 1.04, 5.22) than with IVF/ICSI singleton pregnancy. No statistical differences were noted in any other measured outcomes between the groups.

CONCLUSION(S)

The perinatal outcomes of PGT and IVF/ICSI singleton pregnancies were similar except for the observed potentially higher risk of gestational hypertension with PGT singleton pregnancy. However, because the data on PGT singleton pregnancies are limited, this conclusion warrants further investigation.