Ovulation disorders that inhibit the normal frequency of ovulation, including polycystic ovary syndrome (PCOS), hypothalamic dysfunction, premature ovarian failure, and elevated prolactin
Damaged fallopian tubes due to pelvic inflammatory disease or previous abdominal or pelvic surgery.
Endometriosis when tissue that normally grows in the uterus implants and grows in other locations.
Uterine or cervical causes can interfere with implantations and/or increase the risk of miscarriage (e.g. benign polyps of tumors in the uterus, abnormally shaped uterus, narrowing of the cervix)