Similar to environmental factors, EDCs (endocrine-disrupting chemicals) can influence gene expression without modifying the DNA sequence. It is commonly accepted that the transgenerational inheritance of parentally acquired traits is conveyed by epigenetic alterations also known as “epimutations”. DNA methylation, acetylation, histone modification, RNA-mediated effects and extracellular vesicle effects are the mechanisms that have been described so far to be responsible for these epimutations. They may lead to the transgenerational inheritance of diverse phenotypes in the progeny when they occur in the germ cells of an affected individual. While EDC-induced health effects have dramatically increased over the past decade, limited effects on sperm epigenetics have been described. However, there has been a gain of interest in this issue in recent years. The gametes (sperm and oocyte) represent targets for EDCs and thus a route for environmentally induced changes over several generations. This review aims at providing an overview of the epigenetic mechanisms that might be implicated in this transgenerational inheritance.

After more than four decades of assisted reproductive technology (ART) practice worldwide, today more than 60% of women undergoing in vitro fertilization (IVF) treatments fail to become pregnant after the first embryo transfer and nearly 20% of patients are suffering from unexplained recurrent implantation failures (RIFs) and repeated pregnancy loss (RPL). The literature reported different causes of RIF–RPL, mainly multifactorial, endometrial and idiopathic. RIF remains a black box because of the complicated categorization and causes of this physio-pathological dysregulation of implantation and pregnancy process after ovarian stimulation. Many options were suggested as solutions to treat RIF–RPL with controversial results on their usefulness. In this article, we reviewed different possible therapeutic options to improve implantation rates and clinical outcomes. Based on our experience we believe that endometrium immunomodulation after intrauterine insemination of activated autologous peripheral blood mononuclear cells (PBMCs) or platelet-rich plasma (PRP) can be a promising therapeutic solution. On the other hand, peripheral lymphocyte balance typing, specific cytokines and interleukins profiling can be proposed as predictive biomarkers of implantation before embryo transfer.

Advanced age has been reported to negatively affect sperm parameters and spermatozoa DNA integrity. A decline in sperm criteria was also associated with altered epigenetic marks such as DNA methylation with a potential downstream impact on in vitro fertilization success and clinical outcomes. The aim of the present retrospective study was to clarify the association between advanced paternal age (APA) and sperm parameters, DNA integrity and DNA methylation profile. A total of 671 patients consulting for infertility underwent sperm analysis, sperm DNA integrity assessment and methylation level measurement. The principal finding was that individuals over 40 years of age exhibit a significant increase in DNA fragmentation levels compared to the younger group (15% versus 9%, respectively, p = 0.04). However, there was no significant difference in DNA decondensation and sperm parameters in association with APA. In addition, a drop in the global methylation level was also found in men over 40 years (6% in the young group versus 2% in the old group, p = 0.03). As a conclusion, men over 40 years are at higher risk of elevated sperm DNA fragmentation and lower methylation level. Based on these observations, it is recommended that the assessment of sperm DNA fragmentation should be taken into consideration particularly after the age of 40. Our findings support the idea that paternal age is a crucial factor that should not be neglected during fertility evaluation and treatment since it is associated with epigenetics changes in sperm. Although the underlying mechanism remains to be clarified, we believe that environmental and professional exposure factors are likely involved in the process.

In patients treated with IVF, the incidence of poor ovarian response (POR) after ovarian stimulation varies from 9 to 25 %. However, at present, there are no clear guidelines for treating these poor responders. This study was designed to compare two different ovarian stimulation protocols and addresses future perspectives in the management of these unfortunate patients. Four hundred and forty poor responders were studied during their second IVF cycle. They had all failed to become pregnant during their first IVF cycle where the long GnRH-agonist stimulation protocol (P1) was used. Patients were prospectively randomly assigned to 2 protocol groups (P2 or P3, 220 patients in each arm) at the start of ovarian stimulation according to the order of entry into the study including one patient per each stimulation protocols: The P2 group was treated with a contraceptive pill + flare-up GnRH-agonist protocol and the P3 group with the GnRH-antagonist protocol. The ovarian stimulation characteristics as well as the clinical and ongoing pregnancy rates were compared. Although the numbers of embryos obtained and transferred were significantly higher with the P2 protocol, the implantation and ongoing pregnancy rates per transfer were the same in the two studied groups (8.9 % versus 14.6 % and 8.4 % versus 14.2 % for the P2 and P3 protocols, respectively). Good prognostic factors for ongoing pregnancy with both protocols were: a maternal age <36, no tobacco consumption, a total dose of gonadotropins injection 10 mm. In poorly responding patients treated with IVF, the implantation and ongoing pregnancy rates per transfer were not significantly different between the two protocols studied: contraceptive pill + flare-up GnRH-agonist protocol and the GnRH-antagonist protocol. It is suggested that current strategies for the management of poor responders be reconsidered in the light of the potential contribution of age and the effect of life style changes on fertility potential. A customised policy of ovarian stimulation in these patients including mild stimulation protocols, sequential IVF cycles, oocytes-embryos freeze all protocols and blastocyst transfers after screening may improve the clinical outcome.