Vitrification and the demise of fresh treatment cycles in ART

Contributing factors for pregnancy outcomes in women with PCOS after their first FET treatment: a retrospective cohort study

OBJECTIVE

We aim to explore the contributing factors of clinical pregnancy outcomes in PCOS patients undergoing their first FET treatment.

METHODS

A retrospective analysis was conducted on 574 PCOS patients undergoing their first FET treatment at a private fertility center from January 2018 to December 2021.

RESULTS

During the first FET cycle of PCOS patients, progesterone levels (aOR 0.109, 95% CI 0.018-0.670) and endometrial thickness (EMT) (aOR 1.126, 95% CI 1.043-1.419) on the hCG trigger day were associated with the clinical pregnancy rate. Similarly, progesterone levels (aOR 0.055, 95% CI 0.007-0.420) and EMT (aOR 1.179, 95% CI 1.011-1.376) on the hCG trigger day were associated with the live birth rate. In addition, AFC (aOR 1.179, 95% CI 1.011-1.376) was found to be a risk factor for preterm delivery.

CONCLUSIONS

In women with PCOS undergoing their first FET, lower progesterone levels and higher EMT on hCG trigger day were associated with clinical pregnancy and live birth, and AFC was a risk factor for preterm delivery. During FET treatment, paying attention to the patient's endocrine indicators and follicle status may have a positive effect on predicting and improving the pregnancy outcome of PCOS patients.

Long-term health risk of offspring born from assisted reproductive technologies

Since the world's first in vitro fertilization baby was born in 1978, there have been more than 8 million children conceived through assisted reproductive technologies (ART) worldwide, and a significant proportion of them have reached puberty or young adulthood. Many studies have found that ART increases the risk of adverse perinatal outcomes, including preterm birth, low birth weight, small size for gestational age, perinatal mortality, and congenital anomalies. However, data regarding the long-term outcomes of ART offspring are limited. According to the developmental origins of health and disease theory, adverse environments during early life stages may induce adaptive changes and subsequently result in an increased risk of diseases in later life. Increasing evidence also suggests that ART offspring are predisposed to an increased risk of non-communicable diseases, such as malignancies, asthma, obesity, metabolic syndrome, diabetes, cardiovascular diseases, and neurodevelopmental and psychiatric disorders. In this review, we summarize the risks for long-term health in ART offspring, discuss the underlying mechanisms, including underlying parental infertility, epigenetic alterations, non-physiological hormone levels, and placental dysfunction, and propose potential strategies to optimize the management of ART and health care of parents and children to eliminate the associated risks. Further ongoing follow-up and research are warranted to determine the effects of ART on the long-term health of ART offspring in later life.

Follicle-stimulating hormone (and luteinizing hormone) in ovarian stimulation: Does the dose matter for cycle success?

In this review, we have summarized the evolution in our understanding of a relevance of gonadotropin dosing for cycle outcomes in women attempting to conceive through the utilization of the in vitro fertilization technology.

Prolong cryopreservation duration negatively affects pregnancy outcomes of vitrified-warmed blastocyst transfers using an open-device system: A retrospective cohort study

OBJECTIVE

To investigate the impact of cryopreservation (CP) duration on pregnancy outcomes of vitrified-warmed blastocysts transfers using an open-device liquid-nitrogen (LN₂) system.

METHODS

This retrospective cohort study was conducted on 6327 first vitrified-warmed single blastocyst transfer cycles with autologous oocytes from January 2015 to December 2020. The CP duration was initially divided into six groups: Group I: 0-3 months (n = 4309); Group II: 4-6 months (n = 1061); Group III: 7-12 months (n = 304); Group IV: 13-24 months (n = 113); Group V: 25-72 months (n = 466); Group VI: 73-120 months (n = 74). Multivariate logistic regression was performed to evaluate the independent effect of CP duration on pregnancy outcomes. To further examine the time limit of vitrification, propensity score matching (PSM) was applied to compare pregnancy outcome of patients with storage duration of 25-120 months to those of 0-24 months. After that, pregnancy outcomes were compared among the subgroups of Group I': 0-24 months, Group II': 25-48 months, Group III': 49-72 months, Group IV': 73-120 months. Stratification analysis based on embryo quality was also performed. Primary outcomes were clinical pregnancy rate and live birth rate. Secondary outcomes were implantation, biochemical pregnancy rate, ongoing pregnancy rate and early miscarriage rate.

RESULTS

Logistic regression demonstrated that the odds of pregnancy outcomes were similar across Group I to IV. However, the implantation rate, chances of biochemical pregnancy, clinical pregnancy, ongoing pregnancy, and live birth significantly decreased as the storage duration increased up to 25 months, while miscarriage rate did not significantly differ between groups. Subgroup analysis confirmed a dramatical decrease of clinical pregnancy and live birth rate when cryopreserved for more than 24 months. After that, the slope was relatively steady between 25 and 72 months, then steeply decreased again as CP reached 73-120 months. In addition, there was a more remarkable decline of pregnancy outcomes in the average quality embryo transfers than in the high quality embryo transfers as cryopreservation storage increased.

CONCLUSION

Prolonged cryopreservation of vitrified blastocysts in an open-device LN₂ system up to 24 months might negatively affect pregnancy outcomes. This negative impact progresses as storage duration increases, especially when exceeds 72 months. Average quality embryo appears to be less sustainable with long-term cryo-storage.

Advantages of vitrification preservation in assisted reproduction and potential influences on imprinted genes

Cryopreservation has important application in assisted reproductive technology (ART). The vitrification technique has been widely used in the cryopreservation of oocytes and embryos, as a large number of clinical results and experimental studies have shown that vitrification can achieve a higher cell survival rate and preimplantation development rate and better pregnancy outcomes. Ovarian tissue vitrification is an alternative method to slow freezing that causes comparatively less damage to the original follicular DNA. At present, sperm preservation mainly adopts slow freezing or rapid freezing (LN2 vapor method), although the vitrification method can achieve higher sperm motility after warming. However, due to the use of high-concentration cryoprotectants and ultra-rapid cooling, vitrification may cause strong stress to gametes, embryos and tissue cells, resulting in potentially adverse effects. Imprinted genes are regulated by epigenetic modifications, including DNA methylation, and show single allele expression. Their accurate regulation and correct expression are very important for the placenta, fetal development and offspring health. Considering that genome imprinting is very sensitive to changes in the external environment, we comprehensively summarized the effect of cryopreservation—especially the vitrification method in ART—on imprinted genes. Animal studies have found that the vitrification of oocytes and embryos can have a significant impact on some imprinted genes and DNA methylation, but the few studies in humans have reported almost no influence, which need to be further explored. This review provides useful information for the safety assessment and further optimization of the current cryopreservation techniques in ART.

Shared intent in third-party donation will underpin the success of new surrogacy laws

The demands for surrogacy treatments continue to grow worldwide. However the legal guidance for non-commercial surrogacy treatments remains inadequate, and this commentary argues how the forthcoming guidance on surrogacy from the UK Law Commissions would benefit from a bold decision based on previous experience derived from similar developments in three other areas of assisted conception.

First clinical report of 179 surrogacy cases in the UK: implications for policy and practice

RESEARCH QUESTION

What implications for policy and practice can be derived from outcomes and trends observed across 8 years of a surrogacy programme in two UK-regulated IVF centres (London, Cardiff)?

DESIGN

Retrospective cohort study analysing surrogacy treatments undertaken between 2014 and September 2021.

RESULTS

Surrogacy continues to rise in popularity in the UK despite the inability of those supporting safe and professional practice to advertise to recruit surrogates. In two IVF centres regulated by the Human Fertilisation and Embryology Authority (HFEA), both the number of surrogacy treatments and the proportion of those undertaken on behalf of same-sex male intended parents increased year on year in the period studied. From a cohort of 108 surrogates, 71 babies were born to 61 surrogates (with five pregnancies ongoing) by February 2022. No statistically significant difference in live birth rates (LBR) was observed between the heterosexual couples and same-sex male couples. Sample sizes of single and transgender intended parents were too small (n < 5) to compare. The use of vitrified oocytes in surrogacy treatments has increased year on year, while fresh oocyte use has declined since peaking in 2019. There was no significant difference in LBR between fresh and vitrified oocyte usage across the cohort.

CONCLUSIONS

The number of surrogacy treatments steadily increased, with clear evidence that the proportion of same-sex male couples accessing surrogacy is a major contributor to this growth. Vitrified/warmed oocyte use now outstrips the use of fresh oocytes in the surrogacy treatment cycles studied here. The results represent a strong basis for supporting the liberalization of regulatory reform expected to be introduced in the UK later in 2022.

Electrically-driven handling of gametes and embryos: taking a step towards the future of ARTs

Electrical stimulation of gametes and embryos and on-chip manipulation of microdroplets of culture medium serve as promising tools for assisted reproductive technologies (ARTs). Thus far, dielectrophoresis (DEP), electrorotation (ER) and electrowetting on dielectric (EWOD) proved compatible with most laboratory procedures offered by ARTs. Positioning, entrapment and selection of reproductive cells can be achieved with DEP and ER, while EWOD provides the dynamic microenvironment of a developing embryo to better mimic the functions of the oviduct. Furthermore, these techniques are applicable for the assessment of the developmental competence of a mammalian embryo in vitro. Such research paves the way towards the amelioration and full automation of the assisted reproduction methods. This article aims to provide a summary on the recent developments regarding electrically stimulated lab-on-chip devices and their application for the manipulation of gametes and embryos in vitro.

It is not worth postponing frozen embryo transfers after oocyte pickup: A retrospective cohort study based on propensity score matching

This study was to explore whether postponing frozen embryo transfers (FET) after oocyte pickup (OPU) improves clinical and neonatal outcomes. From May 2018 to Dec 2020, a total of 1109 patients underwent their first OPU cycles adopting a non-selective freeze-all policy were included in this retrospective cohort study. In the immediate group (n=219), patients underwent FET in the first menstrual cycle after OPU, and patients in the postponed group (n=890) waited for more than 1 menstrual cycle after OPU to perform FET. A propensity score matching (PSM) model was used to evaluate the clinical outcomes and neonatal outcomes between the two groups. There were 209 patients in the immediate group and 499 patients in the postponed one after PSM. Patients waited for a significantly shorter period for FET in the immediate group (30.74 ± 3.85 days) compared with the postponed group (80.39 ± 26.25 days, P<0.01). The clinical pregnancy rate (CPR) and live birth rate (LBR) in the immediate group were 58.4% and 48.3%, respectively, which were comparable to those of the postponed one (58.1%, 49.7%, P > 0.05). No statistical significance was found in the average birth weight (3088.82 ± 565.35 g vs 3038.64 ± 625.78 g, P > 0.05) and height (49.08 ± 1.87 cm vs 49.30 ± 2.52 cm) of neonates between the two groups. The gender ratio, the incidence of macrosomia and low birth weight did not differ significantly between the two groups. In conclusion, postponing FET does not improve clinical and neonatal outcomes. If patients have no contraindications, FETs should be carried out immediately after OPU.

Antifreeze proteins for low-temperature preservation in reproductive medicine: A systematic review over the last three decades

Antifreeze proteins (AFPs) are synthesized by diverse non-mammalian species, allowing them to survive in severely cold environments. Since the 1990s, the scientific literature reports their use for low-temperature preservation of germplasm. The aim of this systematic review was to compile available scientific evidence regarding the use of AFP for low-temperature preservation of several reproductive specimens. Internet databases were consulted using the terms: "antifreeze protein" OR "AFP" OR "antifreeze glycoprotein" OR "AFGP" OR "ice-binding protein" OR "IBP" OR "thermal hysteresis protein" AND "cryopreservation". From 56 articles, 87 experiments testing AFPs in low-temperature preservation of gametes, embryos or reproductive tissues/cells were fully analyzed and outcomes were annotated. A positive outcome was considered as a statistically significant improvement on any parameter evaluated after low-temperature preservation with AFP, whereas a negative outcome included worsening of any evaluated parameter, in comparison to untreated groups or groups treated with a lower concentration of AFP. The findings indicated that research on the use of AFP as a cryoprotectant for reproductive specimens has increased markedly over the past decade. Some experiments reported both positive and negative results, which depended, on AFP concentration in the preservation media. Variation in the outcomes associated with species was also observed. Among the 66 experiments conducted in mammals, 77.3% resulted in positive, and 28.8% in negative outcomes after the use of AFP. In fishes, positive and negative outcomes were observed in 71.4% and 33.3% of 21 experiments, respectively. Most positive outcomes included preserving cell post-warming survival. The beneficial effect of AFP supports its use in cryobiological approaches used in human and veterinary medicines and animal protein industry. Moreover, combination of different AFP types, or AFP with antioxidants, or even the use of AFP-biosimilar, comprise some promising approaches to be further explored in cryopreservation.

Factors predicting clinical outcomes from 494 vitrified oocyte donation cycles at a UK-regulated egg bank

RESEARCH QUESTION

Do donor age, AMH, AFC, BMI and reproductive history predict response to ovarian stimulation? Do donor and recipient clinical markers and embryology parameters predict recipient pregnancy and live birth?

DESIGN

Retrospective cohort study of 494 altruistic oocyte donors aged 18-35 years; 340 were matched to 559 recipients. Predictors of donor total oocyte yield and total mature oocyte yield were identified. Total and mature oocyte number were compared according to stratified donor AMH and age. Donor, recipient and embryology parameters predictive of recipient primary outcomes (clinical pregnancy and live birth) were identified.

RESULTS

Donor age and AMH predicted total oocyte yield (P = 0.030 and P < 0.001)) and total mature oocyte yield (P = 0.011 and P < 0.001). Donors aged 30-35 years with AMH 15-29.9 pmol/l had lower total oocyte yield (P = 0.004) and mature oocyte yield (P < 0.001) than donors aged 18-24 years. Up to an AMH threshold of 39.9 pmol/l, increasing AMH levels predicted higher total oocyte yield (<15 pmol/l versus 15-29.9 pmol/l, P = 0.001; 15-29.9 pmol/l versus 30-39.9 pmol/l, P < 0.001; 30-39.9pmol/l versus ≥ 40 pmol/l, P = 1.0) and mature oocyte yield (<15 pmol/l versus 15-29.9 pmol/l, P = 0.005; 15-29.9 pmol/l versus 30-39.9 pmol/l, P = 0.006; 30-39.9 pmol/l versus ≥40 pmol/l, P = 1.0). In recipients, the rate of transferrable embryos per oocytes received, fertilized and number of embryo transfers needed to achieve the primary outcome were predictors of cumulative clinical pregnancy (P = 0.011, P = 0.017 and P < 0.001) and live birth (P = 0.008, P = 0.012 and P < 0.001) rates. Recipient BMI (P = 0.024) and previous miscarriages (P = 0.045) were predictors of cumulative live birth rate. Donor age 18-22 years was associated with a lower incidence of recipient clinical pregnancy (P = 0.004) and live birth (P = 0.001) after the first embryo transfer versus donor age 23-29 years.

CONCLUSIONS

Donor age and AMH are independent predictors of oocyte yield. Raised recipient BMI and history of miscarriages reduce cumulative live birth rates, which may be increased by selecting donors aged 23-29 years, instead of younger donors.

Optimal Endometrial Preparation Protocols for Frozen-thawed Embryo Transfer Cycles by Maternal Age

This retrospective cohort study aimed to explore the optimal endometrial preparation protocols among different maternal age groups. A total of 16,867 frozen-thawed embryo transfer (FET) cycles were categorized into three groups based on endometrial preparation protocols: Natural cycle (NC n = 3893), artificial cycles (AC, n = 11456) and AC with GnRH-a pretreatment (AC+GnRH-a, n = 1518). To account for repeat cycles, a generalized estimating equation (GEE) method was applied to examine the associations between cycle regimens and pregnancy outcomes. Subgroup analyses were conducted to evaluate the best preparation methods for different maternal age groups. Primary outcomes were live birth and early miscarriage rates. After completing GEE, in overall population, the live birth rate [(NC as reference; AC: adjusted odds ratio (aOR) = 0.837, 95% confidential interval (CI) 0.771-0.908; AC+GnRHa: aOR = 0.906, 95%CI 0.795-1.031)] in NC was significantly higher than that in AC, while comparable that in AC+GnRH-a. The early miscarriage rate (AC: aOR = 1.420, 95%CI 1.225-1.646; AC+GnRHa: aOR = 1.545, 95%CI 1.236-1.931) was significantly lower in NC compared to either AC group. Subgroup analysis showed that in younger women, the incidences of live birth (AC: aOR = 0.900, 95%CI 0.804-1.007; AC+GnRHa: aOR = 1.091, 95%CI 0.904-1.317) were equivalent between groups, with a slightly higher in AC+GnRH-a. Early miscarriage rate (AC: aOR = 1.462, 95%CI 1.165-1.835; AC+GnRHa: aOR = 1.137, 95%CI 0.948-1886) was only significantly lower in NC compared to that in AC. In older women, the live birth rate (AC: aOR = 0.815, 95%CI 0.722-0.920; AC+GnRHa: aOR = 0.759, 95%CI 0.627-0.919) was significantly higher, and early miscarriage rate (AC: aOR = 1.353, 95%CI 1.118-1.638; AC+GnRHa: aOR = 1.704, 95%CI 1.273-2.280) was significantly lower in NC compared to either AC group. Our study demonstrated that NC is associated with lower early miscarriage late in overall IVF population. There is a mild favor of AC+GnRH-a in younger women, while the priority of NC is remarkable in older women. Maternal age should be a considerable factor when determining endometrial preparation method for FET.