This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
What is the common cause of labial fusion in an adult female? 
Select and explain. 
A. Congenital adrenal hyperplasia, B. Fetal exogenous androgen exposure, C. Abdominal wall defects, D. All of the above
A: Congenital adrenal hyperplasia
Answer: A: Congenital adrenal hyperplasia 
Explanation: Labial fusion in adult women is most commonly due to classical congenital adrenal hyperplasia. Other causes include, Fetal exogenous androgen exposure Abdominal wall defects Ref: (2010). Chapter 40. Reproductive Tract Abnormalities. In Cunningham F, Leveno K.J., Bloom S.L., Hauth J.C., Rouse D.J., Spong C.Y. (Eds), Williams Obstetrics, 23e.