International Dexeus Forum - 44th edition

REPRODUCTION > IMPLANTATION FAILURES

“Implantation failures: is the embryo responsible?”

Laura Rienzi, G.EN.E.R.A. Centers for Reproductive Medicine (Italy)

A physiological endometrium during the window of implantation is per se receptive, and if a productive dialogue is established with a competent embryo this would lead to a successful implantation. Nonetheless, most of human embryos are not competent since they either do not reach the blastocyst stage or are energetically and/or chromosomally impaired.


Implantation failures: is the embryo responsible?

The overall success of human reproduction, either spontaneously or after IVF, is highly dependent upon embryonic competence. Indeed, evidences exist to claim that a physiological endometrium during the window of implantation is per se receptive and, if a productive dialogue is established with a competent embryo, this would lead to a successful implantation.

Nonetheless, most of human embryos are not competent since they either do not reach the blastocyst stage or are energetically and/or chromosomally impaired. The reasons for the latter are mainly ascribable to maternal age and the consequences of ageing upon the female gametes and, therefore upon the embryo.

Indeed, advanced woman age-related infertility include reduced ovarian reserve and decreased oocyte/embryo competence due to aging insults, especially concerning an increased incidence of aneuploidies. Age-related chromosomal abnormalities mainly arise because of meiotic impairments during oogenesis, following flawed chromosome segregation patterns such as non-disjunction, premature separation of sister chromatids or the recently-described reverse segregation. The upstream causes of such reduced competence, are probably: mitochondrial dysfunction, shortening of the telomeres, cohesion dysfunction and spindle instability.

Different strategies are proposed in IVF to face these issues: fertility preservation through oocyte cryopreservation to prevent aging; optimization of the ovarian stimulation and enhancement of embryo selection to limit its effects; and oocyte donation to circumvent it. Intriguing perspectives, e.g. non-invasive embryo selection approaches, are also expected as putative future avant-gardes.

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