American Board of Obstetrics & Gynecology (ABOG) Qualifying Practice Exam 2026 – Your Complete All-in-One Guide to Exam Success!

The most common chromosomal abnormality associated with first trimester pregnancy loss is indeed related to trisomy. This is due to the fact that many first trimester miscarriages are attributed to chromosomal abnormalities, and among these, the presence of an additional chromosome—such as in trisomy 13, trisomy 18, and trisomy 21—occurs frequently.

In the early stages of pregnancy, particularly in the first trimester, the genetic integrity of the embryo is crucial for successful implantation and development. When there are chromosomal abnormalities like trisomy, the embryo often cannot sustain a viable pregnancy, leading to miscarriage. Trisomies occur at a higher rate compared to other chromosomal abnormalities, making them the leading cause of early pregnancy loss.

Turner syndrome, characterized by the absence of an X chromosome, often results in non-viable embryos and is less common than the various forms of trisomy. Down syndrome, while it can arise due to trisomy 21, generally occurs at a lower frequency during the first trimester compared to the broader category of trisomies. Similarly, triploidy, which involves having three sets of chromosomes, is also a significant cause of miscarriage but is less common than the overall incidence of trisomies