Conditions necessary for conception: o normal ovarian discharge of eggs o normal semen containing normal sperm o sperm-egg encounter → fertilized egg → uterine cavity o uterus adequately prepared for fertilized egg implantation o common causes of “unexplained” infertility o mild endometriosis o luteal insufficiency (methods of understanding luteal function such as BBT, P measurement are inaccurate) o reduced endometrial tolerance o immunity o abnormal gamete fertilization ability