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
Drug given to reduce uterine contractions during preterm labour with least side effects: 
Select and explain. 
A. Ritodrine, B. Nifidipine, C. Magnessium sulphate, D. Progesterone
B: Nifidipine
Answer: B: Nifidipine 
Explanation: 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)