Effect of hCG on Receptivity of the Human Endometrium

Worldwide, 1 in 12 couples experience difficulty in getting pregnant and seek the help of assisted reproductive technologies (ART) such as in vitro fertilization (IVF-egg is fertilized by sperm outside the body), ovarian stimulation (medications are used to stimulate egg development) and intra-cytoplasmic injection (ICSI-single sperm is injected directly into the egg). Regardless of the ART procedure being performed, the newly fertilized embryo must still implant into the mothers endometrium (inner lining of uterus). This implantation process in humans is surprisingly inefficient and accounts for up to 50% of ART failures. Intrauterine infusion of hCG prior to embryo transfer has recently been shown to increase pregnancy rates but the cellular mechanism for this increase is unknown. Successful implantation requires the newly fertilized embryo and the endometrium develop in a synchronized manner. This coordinated development is accomplished, in part, by proteins secreted by the embryo which circulate throughout the maternal bloodstream and alert the maternal body organs (i.e. ovary, endometrium, breast, ect) that fertilization has occurred. One of the earliest of these secreted proteins is human chorionic gonadotropin (hCG), which is the molecule detected in over-the-counter pregnancy tests. From previous studies, we know that hCG production by the embryo alerts the ovary to continue producing progesterone, a hormone required for pregnancy. However, very little is known about the direct effect of hCG on the endometrium during early pregnancy in humans. Using animal models, hCG has been shown to induce specific changes in the endometrium, suggesting that embryo-derived hCG may be "priming" the endometrium in anticipation of implantation. The goal of this research study is to examine the direct effect of hCG on the human endometrium and see if this "priming effect" is also present in humans. Findings from this research may reveal whether pre-treatment with hCG can