This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'Amniocentesis to detect chromosomal abnormalities can be done as early as \nSelect and explain. \nA. 14th week of gestation, B. 18th week of gestation, C. 22nd week of gestation, D. 26th week of gestation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Amniocentesis: examination of a sample of amniotic fluid makes possible the prenatal diagnosis of chromosomal anomalies and certain metabolic defects; the procedure can be used as early as 14th week of pregnancy when abortion of affected fetus is still feasible.', 'role': 'assistant'}]