Hello dear Understand your concern Following emergency contraception you can use after sex. 1. I Pill: It contain high dose of progesterone. And 95 % effective in preventing the pregnancy if taken with in 24 hour after sex. So use I pill as early as possible after sex. You can also use up to 72 hour after sex. But effective will decrease from 80-85%. It should be taken orally. If you will vomit after taking pill then you have to take another dose of I pill. It also cause temporary disruption of menstrual cycle (withdrawal bleeding and delayed period up to 7 day due to hormonal imbalance) 2. You can also use oral contraceptive pill (mala D, yamini, saheli, mala N)to prevent the pregnancy. Take 4 tablet as early as possible and another 4 tablet after 12 hours. You can use up to 72 hour after sex. But if 72 hour has been crossed then you have to confirm the pregnancy by USG scan if period will be delayed and should be terminated by Using Abortion pill (mifepristone plus misoprostol) under the advice of gynecologist. So no tablet needed before the sex. You can use I pill (as it is better than OCP) after sex to prevent the pregnancy. But it can not be used for regular contraception. For regular contraception, you have to take Birth control pill starting from the first day of period to 21 days of cycle, regular on same time every day. Hope this may help you Best regards Dr. Sagar