Despite recent advances in clinical and laboratory techniques of Assisted Reproductive Technology (ART), the pregnancy rate remains around 30% per cycle. It has been estimated that 50% to 75% of lost pregnancies are due to failure of implantation.

The process of implantation is a locally controlled paracrine/juxtacrine-mediated phenomenon. Successful implantation depends on the synchronized "cross-talk" between a functional blastocyst and a "receptive" endometrium. This process leads to apposition, attachment and invasion of embryos and subsequent normal placentation. So the objective of this study is investigate the impact of intrauterine injection of human chorionic gonadotropin (hCG) at the day of ovum pick-up on implantation and pregnancy rates in patients with recurrent implantation failure.

The endometrium can only support implantation during a discrete period of about 6 to 9 days after LH peak; termed the "window of implantation". During this period endometrial glandular epithelium is differentiated into a highly secretory state with the production of various cytokines and growth factors that facilitate implantation. In fact, several substances secreted from the embryo or the endometrium affect implantation. These include cyclic adenosine monophosphate, relaxin, gonadotropin, prostaglandin E2, and glycoprotein hormones.

Human chorionic gonadotropin (hCG) is the earliest blastocyst-derived signals received by the endometrium; it is transcribed as early as the 2-cell embryo stage. It is produced by the trophectodermal cells of the preimplantation blastocyst. Recent evidence suggests that hCG is also produced by the endometrial epithelial cells during the secretory.

It has been shown that intrauterine injection of hCG before embryo transfer significantly improves pregnancy rates in IVF/ICSI cycles.

Inclusion Criteria:

A- Age between 20 and 35 years old.

B- Patients undergoing ICSI trial after one or more previous failure.

Exclusion Criteria:

A- Females with any local cause, uterine pathology, e.g: uterine myoma or previous myomectomy, endometriosis or the presence of hydrosalpinges.

B- Patients undergoing ICSI trial for the first time.

C- Previous Asherman Syndrome.

one hundred opaque envelopes will be numbered serially and in each envelope the corresponding letter which denotes the allocated group will be put according to randomization table. Then all envelopes will be closed and put in one box. When the first patient arrives, the first envelope will be opened and the patient will be allocated according to the letter inside.