Progesterone of choice in emergency contraception is?

Unprotected intercourse without regard to the time of the month carries an 8% incidence of pregnancy, an incidence that can be reduced to 2% by the use of emergency contraceptives within 72 hours of unprotected intercourse. 0.75 mg levonorgestrel are now approved for postcoital contraception and are available over the counter for women aged >17 years. Levonorgestrel is more effective and is associated with fewer side effects than the combination estrogen-progestin regimens. Basically the methods used interfere with the physiological events before implantation, for e.g. inhibition or delaying of ovulation or interference with postovulatory events necessary for implantation & longevity of the blastocyst. REF : gynecology book of shaw 17th