###Human: I have not got withdrawal bleeding after 10 days of taking Unwanted 72. Why? ###Assistant: Hello. You have rightly taken the emergency contraceptive pill within 72 hours of unprotected intercourse. The success rate of ECP is 99 % and ideally,the withdrawal bleed should start in the next 4 to 7 days, but if it has not yet, then you can opt for a serum beta hCG test after eight days post last intercourse to rule out pregnancy, if any, due to possible emergency contraceptive pill failure. If the hCG levels are less than 3 mIU then you are pregnancy safe else you are pregnant.  If the test is negative then you can safely wait for the menses to return for at least two weeks and then, can get an ultrasound pelvis done to check for endometrial thickness and post that if the endometrial thickness is more than 9 mm then you can opt for a withdrawal bleed with Progesterone.