This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General obstetrics, Subject name: Gynaecology & Obstetrics
Incidence of preterm delivery in twin pregnancy is 
Select and explain. 
A. 25%, B. 50%, C. 75%, D. 100%
B: 50%
Answer: B: 50% 
Explanation: Incidence of preterm in twin pregnancy is 50% Mean gestational age for twins is 37weeks Causes of prematurity: Overdistention of uterus Hydromnios Premature rupture of membranes Ref: Dutta Obs 9e pg 193.