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: Unknown
[{'content': 'Treponema pallidum crosses placenta: \nSelect and explain. \nA. After 36 weeks, B. After 28 weeks, C. After 2nd trimester, D. At any stage of pregnancy', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Transmission of Treponema pallidum from an infected woman to her fetus across the placenta may occur at any stage of pregnancy, but the lesions of congenital syphilis usually develop after-the 4th month of gestation, when "fetal immunologic" competence begins to develop.', 'role': 'assistant'}]