This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraception, Subject name: Gynaecology & Obstetrics
All of the following mechanisms might account for a reduce-risk of upper genital tract infection in users of progestin - releasing lUDs, except: 
Select and explain. 
A. Reduced retrograde menstruation, B. Decreased ovulation, C. Thickened cervical mucus, D. Decidual changes in the endometrium
B: Decreased ovulation
Answer: B: Decreased ovulation 
Explanation: Decreased ovulation does not protect from upper genital tract infection. Also it doesn't inhibit ovulation in all women. THE TEXTBOOK OF GYNAECOLOGY SHEILA BALAKRISHNAN SECOND EDITION PAGE NO 379