The close relationship between cumulus cell function and oocyte developmental competence indicates that analysis of cumulus gene expression is a potential non-invasive method to aid embryo selection and IVF outcome. Cumulus was isolated from 674 oocytes from 75 women undergoing ICSI and gene expression analysed by quantitative RT-PCR. Cumulus expression of cyclooxygenase 2 (PTGS2) was higher with mature oocytes, whereas brain-derived neurotrophic factor (BDNF) was lower when fertilisation was normal. Expression levels of gremlin (GREM1) and BDNF were weak positive and negative predictors of embryo quality respectively. Ranking of GREM1 expression within cohorts of oocytes showed that oocytes associated with the highest GREM1 expression were more likely to be transferred or cryopreserved than discarded (49 vs 33%, P<0.02), although the clinical pregnancy rate was not significantly different. This study demonstrates both the feasibility and difficulties of this method of analysis in the largest such group studied thus far. Novel relationships between BDNF expression and fertilisation were identified, and the potential value of GREM1 expression as a marker of embryo quality supports the further assessment of GREM1 analysis in the context of embryo selection.

The prolonged lockdown of health facilities providing non‐urgent gamete cryopreservation—as currently recommended by many reproductive medicine entities and regulatory authorities due to the SARS‐CoV‐2 pandemic will be detrimental for subgroups of male infertility patients. We believe the existing recommendations should be promptly modified and propose that the same permissive approach for sperm banking granted for men with cancer is expanded to other groups of vulnerable patients. These groups include infertility patients (eg, azoospermic and cryptozoospermic) undergoing medical or surgical treatment to improve sperm quantity and quality, as well as males of reproductive age affected by inflammatory and systemic auto‐immune diseases who are about to start treatment with gonadotoxic drugs or who are under remission. In both scenarios, the “fertility window” may be transitory; postponing diagnostic semen analysis and sperm banking in these men could compromise the prospects of biological parenthood. Moreover, we provide recommendations on how to continue the provision of andrological services in a considered manner and a safe environment. Our opinion is timely and relevant given the fact that fertility services are currently rated as of low priority in most countries.

SummaryVitrification is a highly efficient technique for the cryopreservation of the human embryo. The effect of delayed blastulation may be responsible for implantation failures and negatively affects in vitro fertilization (IVF) outcomes. The current literature displays discordant results; some studies have announced higher pregnancy rates after day 5 (D5) transfer compared with day 6 (D6) transfer, while others have shown equivalent outcomes. In the present study an investigation into the clinical implications of delayed blastulation (D5 versus D6) was carried out. We performed a retrospective study comparing clinical pregnancies and implantation rates following warmed single blastocyst transfer (WSBT). All patients coming for a programmed warmed transfer at Edinburgh Assisted Conception Programme, EFREC, Royal Infirmary of Edinburgh, were included in this study and divided in two groups according to the day of blastocyst vitrification: D5 (n = 1563) and D6 (n = 517). The overall survival rate was 95.0% (1976/2080) with no significant difference between the D5 and D6 groups: 95.3% (1489/1563) and 94.2% (487/517) respectively. WSBT of D6 blastocysts resulted in a lower implantation and clinical pregnancy compared with D5 embryos. The implantation rate (IPR) and clinical pregnancy rate (CPR) were respectively 49.4% and 42.6% for the D5 and 37.4% and 32.2% for the D6 embryos, which was statistically significant. The multiple pregnancy rate was 1.32% (1.14% for D5 vs 1.84% for D6). Although the transfer of D6 vitrified-warmed blastocyst remains a reasonable option, priority to a D5 embryo would reduce the time to successful pregnancy.

SummaryThe optimum oxygen tension for culturing mammalian embryos has been widely debated by the scientific community. While several laboratories have moved to using 5% as the value for oxygen tension, the majority of modern in vitro fertilization (IVF) laboratory programmes still use 20%. Several in vivo studies have shown the oxygen tension measured in the oviduct of mammals fluctuates between 2% and 8% and in cows and primates this values drops to <2% in the uterine milieu. In human IVF, a non-physiological level of 20% oxygen has been used in the past. However, several studies have shown that atmospheric oxygen introduces adverse effects to embryo development, not limited to numerous molecular and cellular physiology events. In addition, low oxygen tension plays a critical role in reducing the high level of detrimental reactive oxygen species within cells, influences embryonic gene expression, helps with embryo metabolism of glucose, and enhances embryo development to the blastocyst stage. Collectively, this improves embryo implantation potential. However, clinical studies have yielded contradictory results. In almost all reports, some level of improvement has been identified in embryo development or implantation, without any observed drawbacks. This review article will examine the recent literature and discusses ongoing efforts to understand the benefits that low oxygen tension can bring to mammal embryo development in vitro.

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