Human Reproduction Update Advance Access published online on June 4, 2007
Human Reproduction Update, doi:10.1093/humupd/dmm011
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The role of the endometrium and embryo in human implantation
1 Department of Obstetrics and Gynecology, University Hospital Schleswig-Holstein, Campus Lübeck, 23538 Luebeck, Germany 2 Department of Reproductive Medicine and Gynecology, University Medical Center, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands 3 Centre of Reproductive Medicine, Dutch-speaking Brussels Free University, Laarbeeklaan 101, B-1090 Brussels, Belgium
To whom correspondence should be addressed at: 4 Correspondence address. Tel: +49-451-5002134; Fax: +49-451-5002139; E-mail: klaus.diedrich{at}uk-sh.de
Despite many advances in assisted reproductive technologies (ART), implantation rates are still low. The process of implantation requires a reciprocal interaction between blastocyst and endometrium, culminating in a small window of opportunity during which implantation can occur. This interaction involves the embryo, with its inherent molecular programme of cell growth and differentiation, and the temporal differentiation of endometrial cells to attain uterine receptivity. Implantation itself is governed by an array of endocrine, paracrine and autocrine modulators, of embryonic and maternal origin. Implantation failure is thought to occur as a consequence of impairment of embryo developmental potential and/or impairment of uterine receptivity and the embryo–uterine dialogue. Therefore a better comprehension of implantation, and the relative importance of the factors involved, is warranted. New techniques for monitoring changes in the endometrium and/or the embryo at the level of gene regulation and protein expression may lead to the identification of better markers for implantation. Moreover, the use of predictive sets of markers may prove to be more reliable than a single marker. Continuing refinements to ART protocols, such as optimizing ovarian stimulation regimens, the timing of human chorionic gonadotrophin injection, or the timing of embryo transfer, should help to increase implantation rates further.
Key words: endometrium / embryo development / implantation / ovarian stimulation
Received on June 6, 2007; revised January 29, 2007; accepted on April 18, 2007