Association between oocyte donors' or recipients' body mass index and clinical outcomes after first single blastocyst transfers-the uterus is the most affected.

OBJECTIVE: To assess whether high body mass index (BMI) in either oocyte donors or recipients is associated with poorer outcomes after the first single blastocyst transfer. DESIGN: Retrospective study including 1,394 first blastocyst single embryo transfers (SETs) conducted by 1,394 recipients during oocyte donation cycles with the gametes retrieved from 1,394 women (January 2019-July 2021). Four BMI clusters were defined for both donors and recipients (underweight: <18.5 kg; normal weight: 18.5-24.9 kg; overweight: 25-29.9 kg; and obese: ≥30 kg). SETTING: Network of private IVF centers. PATIENTS: A total of 1,394 recipients aged 42.4 ± 4.0 and with a BMI of 23.2 ± 3.8 kg/m2, and 1,394 donors aged 26.1 ± 4.2 and with a BMI of 21.9 ± 2.5 kg/m2. INTERVENTION: All oocytes were vitrified at 2 egg banks and warmed at 8 in vitro fertilization clinics that were part of the same network. Intracytoplasmic sperm injection, blastocyst culture, and either fresh or vitrified-warmed SETs were conducted. Putative confounders were investigated, and the data were adjusted through regression analyses. MAIN OUTCOME MEASURES: The primary outcome was the live birth rate (LBR) per SET according to donors' and/or recipients' BMI. The main secondary outcome was the miscarriage rate (<22 gestational weeks) per clinical pregnancy. RESULTS: The LBR per blastocyst SET showed no significant association with donors' BMI. Regarding recipients' BMI, instead, the multivariate odds ratio was significant in obese vs. normal-weight recipients (0.58, 95% confidence interval, 0.37-0.91). The miscarriage rate per clinical pregnancy was also significantly associated with recipients' obesity, with a multivariate odds ratio of 2.31 (95% confidence interval, 1.18-4.51) vs. normal-weight patients. A generalized additive model method was used to represent the relationship between predicted LBR or miscarriage rates and donors' or recipients' BMI; it pictured a scenario where the former outcome moderately but continuously decreases with increasing recipients' BMI to then sharply decline in the BMI range of 25-35 kg/m2. The miscarriage rate, instead, increases almost linearly with respect to both donors' and recipients' increasing BMI. CONCLUSION: Obesity mostly affects the uterus, especially because of higher miscarriage rates. Yet, poorer outcomes can be appreciated already with a BMI of 25 kg/m2 in both oocyte donors and recipients. Finer markers of nutritional homeostasis are therefore desirable; recipients should be counseled about poorer expected outcomes in cases of overweight and obesity; and oocyte banks should avoid assigning oocytes from overweight donors to overweight and obese recipients.

Maternal body mass index associates with blastocyst euploidy and live birth rates: the tip of an iceberg?

RESEARCH QUESTION: Does maternal preconceptional body mass index (BMI) associate with mean blastocyst euploidy rate (m-ER) per patient and live birth rate (LBR) after vitrified-warmed euploid single embryo transfer (SET)? DESIGN: Observational study conducted between April 2013 and March 2020 at a private IVF clinic, involving 1811 Caucasian women undergoing trophectoderm biopsy and comprehensive chromosome testing. The outcomes of 1125 first vitrified-warmed euploid SET were also analysed. Patients were clustered as normal weight (BMI 18.5-25; n = 1392 performing 859 SET), underweight (BMI <18.5; n = 160 performing 112 SET) and overweight (BMI >25; n = 259 performing 154 SET). m-ER per patient was the primary outcome. The secondary outcomes were all clinical outcomes per euploid SET. All data were adjusted for confounders through regression analyses. RESULTS: The m-ER per patient decreases as maternal BMI increases from 17 up to 22-23 before reaching a plateau. A linear regression adjusted for maternal age confirmed this moderate association (unstandardized coefficient B: -0.6%, 95% confidence interval [CI]: -1.1 to -0.1%, P = 0.02). All clinical outcomes were similar between normal weight and underweight women. Overweight women, instead, showed higher miscarriage rate per clinical pregnancy (n = 20/75, 26.7% versus n = 67/461, 14.5%; odds ratio [OR] adjusted for blastocyst quality and day of full blastulation: 2.0, 95% CI: 1.1-3.6, P = 0.01) and lower LBR per SET (n = 55/154, 35.7% versus n = 388/859, 45.2%; OR adjusted for blastocyst quality and day of full blastulation: 0.67, 95% CI: 0.46-0.96, P = 0.03). CONCLUSION: These data indicate a need for future research on more sensitive metrics to assess body fat mass and distribution, as well as on the mechanisms leading to lipotoxicity, thereby impairing embryo competence and/or endometrial receptivity. Overweight women should be informed of their higher risk for miscarriage and, whenever possible, encouraged to lose weight, especially before transfer.

TERRA: A Novel Biomarker of Embryo Quality and Art Outcome.

Telomeres are considered to be an internal biological clock, and their progressive shortening has been associated with the risk of age-related diseases and reproductive alterations. Over recent years, an increasing number of studies have focused on the association between telomere length and fertility, identifying sperm telomere length (STL) as a novel biomarker of male fertility. Although typically considered to be repeated DNA sequences, telomeres have recently been shown to also include a long non-coding RNA (lncRNA) known as TERRA (telomeric repeat-containing RNAs). Interestingly, males with idiopathic infertility show reduced testicular TERRA expression, suggesting a link between TERRA and male fertility. The aim of this study was to investigate the role of seminal TERRA expression in embryo quality. To this end, STL and TERRA expression were quantified by Real Time qPCR in the semen of 35 men who underwent assisted reproductive technologies (ART) and 30 fertile men. We found that TERRA expression in semen and STL was reduced in patients that underwent ART (both p < 0.001). Interestingly, TERRA and STL expressions were positively correlated (p = 0.010), and TERRA expression was positively associated with embryo quality (p < 0.001). These preliminary findings suggest a role for TERRA in the maintenance of sperm telomere integrity during gametogenesis, and for the first time, TERRA expression was found as a predictive factor for embryo quality in the setting of assisted reproduction.

The Impact of Unbalanced Maternal Nutritional Intakes on Oocyte Mitochondrial Activity: Implications for Reproductive Function.

Accumulating evidence on the effect of nutrition on reproduction is emerging from both animal and human studies. A healthy dietary pattern and nutrient supplementation, especially during the peri-conceptional period, might be helpful to achieve a live birth, although the mechanisms implicated are not fully understood. The endocrine system and the ooplasmic organelles apparatus, in particular the mitochondria, are clearly key elements during oogenesis and subsequent embryo development, and their proper functioning is associated with nutrition, even beyond maternal aging. Several studies in animal models have reported various adverse effects on mitochondria caused by unbalanced dietary intakes such as high fat diet, high fat high sugar diet, and low protein diet. The alterations produced might include mitochondrial intracellular distribution, content, structure, biogenesis, and functioning. This review summarizes the key role of mitochondria in female reproduction and the effects of different dietary macronutrient compositions on oocyte mitochondrial activity with their possible short-, medium-, and long-term effects.

Endometriosis shows no impact on the euploid blastocyst rate per cohort of inseminated metaphase-II oocytes: A case-control study.

OBJECTIVE: To evaluate the true impact of endometriosis on oocytes' competence defined as blastulation, euploidy and implantation rates. DESIGN: Retrospective multicenter case-control study involving infertile couples undergoing ICSI with qPCR and trophectoderm biopsy-based PGT-A. Patients affected from endometriosis (n = 210) were diagnosed through transvaginal sonography or surgical history with histological confirmation. Each case was matched to two controls (n = 420) according to IVF clinic, maternal age at retrieval (38.6 ± 2.7 yr), number of previous failed IVF treatments (0.5 ± 0.8) and number of metaphase-II oocytes retrieved (6.1 ± 3.7 per patient). The primary outcome was the mean euploid blastocyst rate per cohort of inseminated metaphase-II oocytes. Other embryological, clinical, obstetric and neonatal outcomes were also evaluated. RESULTS: The mean euploid blastocyst rate per cohort of inseminated metaphase-II oocytes was identical in the two groups (18 %±22 %) independently of maternal age. No difference was shown for all embryological outcomes investigated. The live birth rates per vitrified-warmed single euploid blastocyst transfer were also similar (67/158, 42 % in patients affected from endometriosis versus 132/327, 40 % in matched-controls). No difference was reported in the gestational and neonatal outcomes. The cumulative live birth delivery rates among completed cycles were also identical (61/201, 30 % versus 117/391, 30 % in endometriosis and matched-control groups, respectively) independently of maternal age. CONCLUSIONS: Endometriosis might not impair oocyte developmental and reproductive competence, although its potential impact on the number of metaphase-II oocytes retrieved cannot be ignored. This information is critical for clinicians during counseling to outline an effective strategy to treat infertile patients affected from this condition. Future prospective studies are needed to evaluate the impact of endometriosis stage on euploidy rates.

Type of protein supplement in cryopreservation solutions impacts on the degree of ultrastructural damage in frozen-thawed human oocytes.

Protein sources used as supplements of IVF culture media are known to have several implications for the function and stability of embryo culture environment. In fact, they i) transport biologically active molecules ii) chelate heavy metals, iii) regulate media pH, iii) scavenge reactive oxygen species (ROS) and iv) attenuate osmotic stress to which cells are exposed in sub-optimal culture conditions. Instead, their specific relevance to the formulation of cryopreservation solutions used for gamete and embryo cryopreservation remains uncertain. In the present work, we tested the hypothesis that different protein supplements present in cryopreservation solutions, serum or plasma protein solution (PPS), or different concentrations of the same supplement (serum), are associated with different types and/or magnitude of cryopreservation-derived cell damage. To this end, using cryopreservation solutions containing serum or PPS, donated supernumerary human mature oocytes were frozen-thawed by slow freezing and compared with fresh controls. Ultrastructural markers of oocyte quality were adopted as objective measure to assess possible damage from cryopreservation. The study results indicate that the adoption of serum minimises cell damage induced by cryopreservation. Indeed, typical hallmarks of cryodamage in human oocytes, i.e. loss of cortical granules, zona pellucida hardening and above all vacuolization, were largely reduced in oocytes cryopreserved with solutions containing serum, especially if used a higher concentration. This suggest that oocyte cryopreservation still has significant margins of improvement that may derive also from composition of cryopreservation media.

A brief history of oocyte cryopreservation: Arguments and facts.

The term "cryopreservation" refers to the process of cooling cells and tissues and storing them at subzero temperatures in order to stop all biological activity and preserve their viability and physiological competences for future use. Cooling to subzero temperatures is not a physiological condition for human cells; this is probably due to the high content of water in the living matter, whose conversion to ice crystals may be associated with severe and irreversible damage. Among reproductive cells and tissues, metaphase II oocytes are notably vulnerable to cryopreservation, mainly because of their large size, low surface area to volume ratio, relatively high water content and presence of the meiotic spindle. As human biological systems lack efficient internal defense mechanisms against chilling injuries, it is of the utmost importance to supply adequate external support, in terms of cryoprotectant additives, appropriate cooling/warming rates, and suitable long-term storage. Over the years, scientists have proposed different cryopreservation strategies in the effort to achieve an optimized recipe ensuring cell survival and, at the same time, maintenance of the physiological functions and abilities necessary to continue life. However, despite the first success obtained in the 1980s with frozen oocytes, it was not until recently that notable improvements in the cryopreservation technique, thanks to the advent of vitrification, allowed a breakthrough of this fine procedure.

Perspectives in Gamete and Embryo Cryopreservation.

Cryopreserved gametes and embryos are a major feature of human-assisted reproduction and patient care services, accounting for an increasing number of births worldwide. Since the first success obtained using frozen human spermatozoa, cryopreservation technology has been successfully extended to include oocytes and embryos, in a variety of both medical and nonmedical indications. Over the years, the available procedures have become widely implemented and the increasing evidence of its efficacy has contributed to acceptance of the technology. Nevertheless, a gold standard protocol that would be universally shared by clinics has yet to be definitively established and, therefore, research into cryopreservation of gametes and embryos cannot be considered concluded. Moreover, much effort should be committed to the definition and resolution of safety issues, the establishment of automation, and investigations about the potentiality of immature germ cells or stem cells.

The worldwide frozen embryo reservoir: methodologies to achieve optimal results.

Cryopreservation of the human embryo has been successfully achieved at the zygote (day 1), cleavage (day 2/3), and blastocyst (day 5) stages; however, each stage presents specific advantages and disadvantages. During the past decades, two major methods have been applied: slow freezing (equilibrium procedure) and vitrification (nonequilibrium procedure). The overwhelming majority of published data prove that the latest vitrification methods induce less cellular trauma and are a more effective cryopreservation technique of human embryos than any other versions of slow freezing. For this reason, fragmented and slow-cleaving embryos that normally would not be recommended may be revaluated for cryopreservation by using the vitrification method. Furthermore, if laser-assisted necrotic blastomere removal is associated with the slow-freezing/thawing procedure, good clinical results can be obtained. Finally, the most proper embryo cleavage stage at which to perform cryopreservation has to be assessed according to clinical indications and laboratory experience.