- 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)