This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Gynae), Subject name: Gynaecology & Obstetrics
[{'content': 'Most common abnormality in first trimester abortion \nSelect and explain. \nA. Defective genes, B. Cervical incompetence, C. Placental & membrane abnormality, D. Retroversion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A. i.e. (Defective genes) (161 - Dutta)* Genetic factor (50%) of early miscarriage are due to chromosomal abnormality in the conceptus. Autosomal trisomy is the commonest (50%) cytogenic abnormality in FIRST TRIMESTER*** Cervical incompetence (congenital or acquired) is the most common abnormality in SECOND TRIMESTER*** The cause of fetal death in ectopic pregnancy is postulated as vascular accident*** Most valuable diagnostic test in a case of suspected ectopic pregnancy is - Transvaginal USG**', 'role': 'assistant'}]