This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Complication of 3rd Stage of Labour, Subject name: Gynaecology & Obstetrics
Common cause of retained placenta: 
Select and explain. 
A. Atonic uterus, B. Constriction ring, C. Placenta accreta, D. Poor voluntary expulsive effort
A: Atonic uterus
Answer: A: Atonic uterus 
Explanation: Ans. is a, i.e. Atonic uterusRef. JB Sharma Obs, Pg 343M/C cause of retained placenta is a simply adherent placenta. This is due to mainly atonic uterus.