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: Pediatrics
Which of the following is the least common cause of ambiguous genitalia in a female child? 
Select and explain. 
A. Fetal placental steroid sulfatase deficiency, B. Fetal placental aromatase deficiency, C. Congenital adrenal hyperplasia, D. WNT-4 gene mutation
A: Fetal placental steroid sulfatase deficiency
Answer: A: Fetal placental steroid sulfatase deficiency 
Explanation: Fetal placental steroid sulfatase deficiency is an X-linked disorder therefore occur only in males. So it's the least common cause of ambiguous genitalia in a female child. Ref: Principles and practice of endocrinology and metabolism, Page 957 By Kenneth L. Becker page1061.