Recurrent pregnancy loss (RPL) is a distressing condition defined by two or more consecutive miscarriages before 20 weeks of pregnancy. The causes of RPL are diverse, reflecting the complexity of reproductive biology and the many factors that can influence pregnancy maintenance. Understanding these causes is essential for effective evaluation and treatment.
1. Unexplained Causes (Including Non-APS Thrombophilias)
In about 50% of cases, no clear cause is identified despite thorough evaluation. Some women may have inherited or acquired thrombophilias (blood clotting disorders) that are not related to antiphospholipid syndrome (APS), which may contribute to miscarriage risk.
2. Endocrine Factors
Hormonal imbalances such as uncontrolled diabetes, thyroid dysfunction, polycystic ovary syndrome (PCOS), luteal phase defects, and hyperprolactinemia can disrupt the hormonal environment necessary for pregnancy maintenance.
3. Autoimmune Causes
Autoimmune disorders, especially antiphospholipid antibody syndrome (APS), affect blood clotting and placental function, increasing miscarriage risk. Other autoimmune antibodies may also play roles, affecting the maternal immune tolerance to pregnancy.
4. Anatomic Abnormalities
Structural issues with the uterus, such as uterine septum, fibroids, polyps, adhesions (Asherman’s syndrome), or congenital malformations, can interfere with implantation or restrict fetal growth.
5. Genetic Factors
Chromosomal abnormalities in either parent or the embryo are a common cause of RPL. Balanced translocations or other chromosomal rearrangements in parents can lead to unbalanced embryos that fail to survive. Embryonic aneuploidies (abnormal chromosome numbers) are increasingly common with advancing maternal age.
6. Infections
Certain infections involving the reproductive tract, such as bacterial vaginosis or chronic endometritis, may contribute to pregnancy loss, though infection is a less frequent cause compared to others.
Conclusion
Recurrent pregnancy loss results from multifactorial causes including genetic, anatomical, endocrine, immunological, and sometimes unexplained factors. A comprehensive workup by fertility specialists aims to identify treatable conditions, offering hope to couples to achieve successful pregnancies with appropriate care and intervention.