What is the most common etiology of spontaneous abortion during the first trimester?

• A. Chromosomal abnormalities
• B. Autoimmune disorders
• C. Infections
• D. Anatomical defects

Answer: (A)

The most common etiology of spontaneous abortion during the first trimester is chromosomal abnormalities. In early pregnancy, particularly in the first trimester, a significant proportion of conceptions are affected by these abnormalities, which can arise from errors in either the egg or sperm. Common types of chromosomal abnormalities include aneuploidy, where there is an improper number of chromosomes, leading to developmental issues that prevent the embryo from implanting or developing normally.

Research indicates that approximately 50-70% of first-trimester miscarriages are due to chromosomal abnormalities, which reflects the body’s ability to detect and reject non-viable pregnancies. This biological mechanism serves as a natural means of ensuring that only those pregnancies with the potential for healthy development continue.

Other factors such as autoimmune disorders, infections, and anatomical defects can contribute to miscarriage but are far less common. Autoimmune disorders, like antiphospholipid syndrome, might cause miscarriages due to immune system dysregulation, but these cases do not account for the majority. Likewise, infections can lead to miscarriage, but specific infectious agents affecting pregnancy are less prevalent compared to chromosomal issues. Anatomical defects, while serious, typically do not emerge as the leading cause of first-trimester loss;