Anatomical issues with the uterus, such as a septate uterus: This condition is a common cause of recurrent miscarriages due to the abnormal shape of the uterus, which can interfere with implantation or growth of the embryo.

Hormonal imbalances, particularly luteal phase defect or polycystic ovary syndrome (PCOS): Hormonal issues can affect the endometrium's ability to support a pregnancy, leading to early miscarriage.
Immunological factors, including antiphospholipid syndrome (APS): APS is an autoimmune disorder that can cause blood clots and miscarriages.
Genetic factors, such as balanced translocations in one of the partners: Carriers of balanced translocations are at increased risk of recurrent miscarriages due to the potential for producing unbalanced gametes.

Antiphospholipid syndrome (APS): Although mentioned earlier, APS is critical to diagnose due to its potential for causing severe thrombotic events and the availability of specific treatments to improve pregnancy outcomes.
Inherited thrombophilias, such as Factor V Leiden or prothrombin gene mutation: These conditions increase the risk of blood clots and can be associated with recurrent miscarriages.

Uterine fibroids: While not uncommon, fibroids causing recurrent miscarriages are less frequently the primary issue compared to other factors.
Endometrial polyps or other endometrial abnormalities: These can interfere with implantation or growth of the embryo but are less common causes of recurrent miscarriages.
Uncontrolled diabetes or thyroid disease: Although these conditions can increase the risk of miscarriage, they are typically identified through abnormal labs, which are not present in this case.