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: Dental
[{'content': 'During pregnancy: \nSelect and explain. \nA. Orthodontic treatment can be carried out without problem, B. Preferably should not be carried out, C. Active movement of teeth should not be done in 2nd trimester, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Finally, although orthodontic treatment can be carried out during pregnancy,\xa0 there are risks involved. Gingival hyperplasia is likely to be a problem, and the hormonal\xa0 variations in pregnancy sometimes can lead to surprising results from otherwise predictable\xa0 treatment procedures. Because of bone turnover issues during pregnancy and lactation, an\xa0 orthodontist theoretically should be vigilant about loss of alveolar bone and root resorption at\xa0 these time-but radiographs to check on the status of bone and tooth roots are not permissible\xa0 during pregnancy. Treatment for a potential patient who is already pregnant should be\xa0 deferred until the pregnancy is completed. If a patient becomes pregnant during treatment,\xa0 the possible problems should be discussed, and it is wise to place her in a holding pattern\xa0 during the last trimester, limiting the amount of active tooth movement.\nRef: Proffit-4th ed pg no 319', 'role': 'assistant'}]