This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abnormal labor, Subject name: Gynaecology & Obstetrics
[{'content': 'Drug given to reduce uterine contractions during preterm labour with least side effects: \nSelect and explain. \nA. Ritodrine, B. Nifidipine, C. Magnessium sulphate, D. Progesterone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Nifidipine which is a calcium channel blocker has the advantage of being effective orally,safe and cheap.Transient hypotension should be looked out for .A Cochrane review found that nifedipine was superior to betamimetics as a tocolytic.But there is no clear first line agent to date .(pg 175 textbook of obstetrics Sheila balakrishnan 2nd edition)', 'role': 'assistant'}]