SummaryHLA-G expression has been detected in early preimplantation embryos and it has been postulated that a relationship between embryonic expression of this factor and successful pregnancy may exist. Forty-six patients were prospectively selected from our centre ‘Unidad de Reproducción Humana, Hospital Universitario de Canarias’ for conducting this study. In all cases, metaphase II (MII) oocytes were fertilized using intracytoplasmic sperm injection 2–4 h after retrieval. Embryos were cultured individually in 20 µl droplets of G-1 medium (VitroLife) under oil at 37°C and a 6% CO2 environment. Fertilization was assessed at 18 h postinsemination and all oocytes fertilized were passed into a new culture plaque individually in 300 µl culture medium until day 3 of culture. The culture medium was examined for the expression and secretion of sHLA-G with a sandwich enzyme-linked immunosorbent assay kit (BioVendor, Heidelberg, Germany) according to the manufacturer’s instructions. We found statistical significance between higher levels of sHLA-G secretion and pregnancy rate. When both groups were compared there was no difference in embryo quality of transferred embryos, but a significant difference in the number of oocytes and the embryo quality of the cohort existed that was greater in the pregnant group. A standardized sHLA-G assay with a specifically defined range and standard units provides a non-invasive method to identify the most competent embryos for transfer.

A little studied aspect of developmental arrest (DA) in ART is zygote arrest (ZA). Etiologically, blockage at the first cleavage stage includes molecular and chromosomal anomalies, some of which manifest morphologically. Given considerations on embryo culture, transfer and cryopreservation, optimal zygote selection is very important. The aim of this study was to ascertain whether zygote morphological features were indicators of increased ZA. In this study we performed a prospective, observational study of 2105 zygotes obtained from consecutive patients who were undergoing IVF/ICSI treatment, of which 43 (2%) suffered ZA. Morphological features observed under the inverted microscope were qualitatively categorized: pronuclear size, nucleolar precursor bodies (NPB) alignment, light and dark halos, polar body placement and fragmentation observed at 16-18 h post-insemination. We compared these features in blocked versus cleaved zygotes at 48 h and found significant correlations (p < 0.05) between ZA and three features: the absence of a light halo (p = 0.001), the absence of a dark halo (p < 0.005), and non-aligned NPB (p < 0.05). We can say that certain morphological features are indicators of significantly increased zygote arrest. These findings may be of utility for optimal zygote selection and culture strategies, especially in countries under restrictive conditions.

Study question In recent decades there has been an increase in environmental contaminants than can affect assisted reproduction techniques. We analyze the influence of vanadium (V) and lead (Pb) on these results. Summary answer Higher seminal fluid V levels affect fertilization rate (FR). Higher Pb and V levels decrease embryo cleavage rate (CR). What is known already Some animal studies have shown that V produces toxicity in the male reproductive system through oxidative stress, and this leads to decreases sperm count and motility, as well increased concentration of abnormal sperm. Pb is one of the main pollutants and, it accumulates in the male reproductive organs, deteriorates the quality of semen, increases the frequency of spontaneous abortion and male infertility. And it has also been seen that it inhibits sperm functions in vitro, although its mechanism of action is still unknown. Study design, size, duration A prospective study was conducted in 102 males, with a mean age of 38.0 ± 5.7, attended successively for initial evaluation, in the Human Reproduction Unit of the Hospital Universitario de Canarias, between february and april 2018, who underwent a semen analysis and metal detection and, subsequently, an IVF/ICSI treatment during years 2019 and 2020 (n = 92). The relationship between the presence of metals and the results of ART has been established. Participants/materials, setting, methods We included two groups based on semen parameters: 41 patients with pathological spermiograms (40.2%), while the remaining 61 (59.8%) had a normal semen analysis and constituted the control group.The study of seminal parameters was performed according to the WHO guidelines. The metals analysis was carried out in the Toxicology Area of the Universidad de La Laguna, using the digestion for microwave method. Metal measurement was performed using inductively coupled plasma optical emission spectrometry (ICP-OES). Main results and the role of chance In our study we have observed 79.4% of patients have V in semen. Significant differences have been found in the concentration of V in semen (t100=1.988, p = 0.05), is higher in patients who drink alcohol (0.51± 0.40 mg/Kg) than in abstinent patients (0.35± 0.30 mg/Kg). The group with FR above 75% presented lower V values compared to those with rates below 75% (p = 0.039). Within this last group, 33.3% present V values higher than 0.7 mg / kg compared to 15.8% who present it in the group with FR greater than 75% (OR = 2.67 CI95% 1.01, 7.52; p = 0.048). A statistical relationship was found between CR and Pb and V. Those who did not reach 100% CR presented higher Pb values (p = 0.052). Of them, 63.6% presented Pb compared to 38.5% in the group reaching 100% division. This same relationship was observed for V, with higher values in the group that did not reach 100% (p = 0.032), and V being present in 90.9% of the samples compared to 79.5% in the group reaching 100%. Limitations, reasons for caution The limitation of this study was the volume of semen that could be obtained for the metal detection, only 0.5 ml. This was because the semen sample was used at the same time to make a diagnosis of infertility though a spermiogram Wider implications of the findings The determination of metals in semen opens a new field in the study of infertility, and many cases of unknown infertility could due to metal presence or absence in seminal fluid, with the option of performing several treatments to correct these possible anomalies. Trial registration number not applicable