This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Contraceptives, Subject name: Gynaecology & Obstetrics
The progesterone component of OCP acts by: 
Select and explain. 
A. Preventing ovulation, B. Inhibiting implantation, C. Bringing about alterations in cervical mucus, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is d, i.e. All of the aboveRef: SK Chaudhary 7th/ed, p125-126,14Actions of the progesterone component of combined oral contraceptives:* Suppresses ovulation by its inhibitory action on the pituitary and the hypothalamus. This is predominantly achieved by estrogens but even by progesterone.* Causes atrophic changes in the endometrium and prevents nidation even if fertilization occurs.* Acts on the cervical mucus, making it thick and tenacious and impenetrable by sperms.The third-generation progestogens have a higher affinity for progesterone receptor and have a role in inhibiting ovulation.The main function of progestogens in combined pills is, to counteract the undesirable effects of estrogen such as endometrial hyperplasia and heavy withdrawal bleeding.