The purpose of this study is to compare gene expression profiles in endometrial biopsies during the window of implantation after triggers of oocyte maturation using GnRH agonist or hCG and compared with their natural cycles in order to identify genes that may be dysregulated in GnRH agonist-triggered cycles. The investigators also intend to evaluate patients feeling of well being and physical quality of life after GnRH agonist trigger compared with hCG trigger.

Ovarian hyperstimulation syndrome (OHSS) is an iatrogenic complication of controlled ovarian hyperstimulation (COH) which may result in significant morbidity and rarely mortality as well as significant financial and psychological distress. The use of a GnRH agonist for induction of final oocyte maturation in ovarian stimulation cycles utilizing GnRH antagonist for pituitary suppression has proven to be an effective method of preventing the risk of OHSS development. Unfortunately, some studies, but not all, have also reported lower pregnancy rates in these cycles as compared to cycles using hCG trigger and this has been attributed to possible impaired endometrial receptivity. The investigators intend to obtain endometrial biopsies collected from the same subject in a natural cycle and then a biopsy during either a GnRH agonist or hCG triggered stimulation. Expression profiles of mRNAs will first be screened using microarray technology. Relative levels of specific mRNAs that display altered expression in the GnRH-triggered samples, as assayed by microarray, will then be confirmed by real-time, quantitative reverse transcription/polymerase chain reaction (Q-PCR). The investigators shall also evaluate patients feeling of well being and physical quality of life after GnRH agonist trigger compared with hCG trigger.