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
Commonest cause of non-engaged head in primi at term is 
Select and explain. 
A. CPD, B. Hydramnios, C. Brow presentation, D. Breech presentation
A: CPD
Answer: A: CPD 
Explanation: Causes of Obstructed labour : CPD Contracted pelvis Cervical dystocia Transverse lie Brow presentation Hydrocephalus Big baby Compound presentation Locked twins Ref: Dutta Obs 9e pg 379.