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: Anatomy
Which of the following trigger onset of labour? 
Select and explain. 
A. ACTH in mother, B. ACTH in fetus, C. Prostaglandin, D. Oxytocin
B: ACTH in fetus
Answer: B: ACTH in fetus 
Explanation: Fetal ACTH acts on fetal adrenal gland causing release of DHEA and DHEA sulphate which are used by the placenta along with the other enzymes like Sulfatase ,Aromatase, 3 B hydroxysteroid dehydrogenase, 17 B hydroxysteroid dehydrogenase -Conveing into Estriol and Estardiol that help in triggering the labour. Ref: Williams Obs 24e pg 108-109.