This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrine System, Subject name: Physiology
Which of the following could inhibit the initiation of labor? 
Select and explain. 
A. Administration of an antagonist of the actions of progesterone, B. Administration of LH, C. Administration of an antagonist of PGE2 effects, D. Mechanically dilating and stimulating the cervix
C: Administration of an antagonist of PGE2 effects
Answer: C: Administration of an antagonist of PGE2 effects 
Explanation: Antagonism of progesterone's effects, dilation of the cervix and oxytocin all increase uterine smooth muscle excitability and facilitate contractions and the onset of labor. LH would have no effect. Prostaglandin E2 strongly stimulates uterine smooth muscle contraction and is formed at an increasing rate by the placenta late in gestation.