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
Which of the following contraceptives can prevent a pregnancy when used alone after an act of unprotected intercourse? 
Select and explain. 
A. Copper IUCD, B. Progesterone or Combined oral contraceptives, C. Mifepristone, D. All of these can work if used within 3 days of Unprotected Intercourse
D: All of these can work if used within 3 days of Unprotected Intercourse
Answer: D: All of these can work if used within 3 days of Unprotected Intercourse 
Explanation: Emergency contraceptives IUCD: Can prevent implantation up till 5th day of unprotected inter-course Progesterone only pill: LNG 1.5 mg :can reduce tubal motility , make endometrium 'Out of Phase" for implantation of embryo Combined Pill: the Yuzpe regimen can prevent embryo implantation since the estrogen component makes the endometrium unreceptive. Mifepristone, Antiprogestin, RU 486, prevents implantation Ulipristal acetate: SPRM: Selective progesterone receptor modulator