The endometrium in human assisted reproduction

Endometrial receptivity and pregnancy outcome

Human implantation is a highly complex and multifactorial process. Successful implantation requires the presence of a healthy embryo, a receptive endometrium, and a synchronized molecular dialogue between the two, as well as immune tolerance/protection from the host. The endometrial receptivity refers to a hormonally limited period in which the endometrial tissue acquires a transient functional status allowing blastocyst implantation and pregnancy initiation. Global knowledge of endometrial receptivity grew up in recent years. Improvements in genetics, new biomarkers, noninvasive methods, new advanced techniques (Endometrial receptivity assay - the ERA system, proteomic analysis) offer the possibility to evaluate the endometrial status and to manage patients with infertility problems, especially women undergoing assisted reproductive treatment. This overview reports the most relevant knowledge and recent advances in the study of implantation processes from the perspective of the endometrium, often considered as being the main barrier for a successful pregnancy initiation. Endometrial receptivity is a topic of great interest and further studies are needed for the early identification of endometrial abnormalities and the discovery of new strategies for increasing the chance for the establishment of pregnancy.

Endometrial Receptivity and its Predictive Value for IVF/ICSI-Outcome

Endometrial receptivity plays a crucial role in the establishment of a healthy pregnancy in cycles of assisted reproduction. The endometrium as a key factor during reproduction can be assessed in multiple ways, most commonly through transvaginal grey-scale or 3-D ultrasound. It has been shown that controlled ovarian hyperstimulation has a great impact on the uterine lining, which leads to different study results for the predictive value of endometrial factors measured on different cycle days. There is no clear consensus on whether endometrial factors are appropriate to predict treatment outcome and if so, which one is suited best. The aim of this review is to summarize recent findings of studies about the influence of endometrial thickness, volume and pattern on IVF- and ICSI-treatment outcome and provide an overview of future developments in the field.

The midluteal decline in serum estradiol levels is drastic but not deleterious for implantation after in vitro fertilization and embryo transfer in patients with normal or high responses

OBJECTIVE

To determine the impact of the peak E(2) level and its midluteal decline on IVF-ET outcome in a group of normal- and high-responding patients.

DESIGN

Retrospective analysis of IVF-ET data.

SETTING

Tertiary-care, university-affiliated teaching hospital.

PATIENT(S)

A total of 100 patients aged </=38 years and receiving up to three embryos per transfer who underwent a similar standard controlled ovarian hyperstimulation for IVF-ET.

INTERVENTION(S)

Morning blood was collected on days 0 (hCG day), +9, and +14.

MAIN OUTCOME MEASURE(S)

Treatment cycle hormonal characteristics and percent midluteal E(2) decline in conception and nonconception cycles.

RESULT(S)

Among all cycles, a mean decline of 95.0% in serum E(2) was observed at the midluteal phase. No significant differences were found in various parameters comparing conception with nonconception cycles. Occurrence of conception did not correlate with the absolute E(2) level or with percent E(2) decline in good and high responders. Early spontaneous abortion occurred more frequently in high responders with >98% E(2) decline; however, the difference did not reach statistical significance.

CONCLUSION(S)

Multifactorial analysis refutes the negative role of supraphysiologic levels of E(2) on the day of hCG administration or its dramatic decline at the midluteal phase on the success rate after embryo transfer. A possibly increased rate of early spontaneous abortion in the high-response group warrants further verification.