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: Gynaecology & Obstetrics
[{'content': 'All of the following statements regarding the mechanism of action of combined oral contraceptive drugs are TRUE, EXCEPT: \nSelect and explain. \nA. Progestins prevent ovulation by suppressing LH release, B. Progestins cause thickening of cervical mucus and prevent sperm passage, C. Estrogen modifies tubal and uterine contractions and prevent feilization, D. Estrogen makes endometrium hyperproliferative and hypersecretory and prevents implantation', 'role': 'user'}, {'content': 'Answer: C \nExplanation: It is the progesterone content and not the estrogen content of OCP which modifies tubal and uterine contractions and prevent feilization. Mechanism of action of OCPs: Inhibition of ovulation: Oestrogen decreases FSH release and progesterone decreases LH release. Progestins cause thickening of cervical mucus and prevent sperm passage Progesterone modifies the tubal and uterine contractions and prevent feilization Failure of implantation: Estrogen makes the endometrium hyperproliferative and hypersecretory, whereas progesterone makes it atrophied and hyposecretory. Ref: Basic Undergraduate Pharmacology By Sudeb Mondal page 247.', 'role': 'assistant'}]