Hello, and I hope I can help you today. Your ovaries swell (even to greater than 10 cm in size) and become very heavy when you have OHSS even though your eggs were harvested. This can make it possible that one of your ovaries fell from it s normal position on either side of you uterus to the area between your uterus and your rectum, called your posterior cul-de-sac. As your ovary decreases in size, the pressure on your rectum should decrease. This diagnosis would be best confirmed by a transvaginal ultrasound. You also may have had some internal bleeding at the time of your ovum harvest which, if it accumulated in the same area behind your uterus, could still cause rectal discomfort until your ovaries return to normal size. I hope this answered your question adequately and that this information was helpful. Best wishes, Dr. Brown