Oral emergency contraceptive pills, which are hormonal in nature, can cause disruptions in the menstrual cycle. Some people may delay their period for 7-10 days, while others may delay it later, perhaps for 15 days or so, because everyone’s body type is different. Menstruation will eventually come, but, it will just come sooner or later. If you have not had your period for more than 10 days, it is best to use an early pregnancy test to rule out the possibility of conception. Since the pill is not 100% contraceptive, there is a 20% chance of failure, so it is important to rule out the possibility of conception. If conception is ruled out and the delay is long, it is recommended to go to the hospital for an ultrasound to see the thickness of the endometrium. If the thickness of the endometrium is above 0.8cm, you can wait for your period without taking any oral medication at this time. If the endometrium is below 0.8cm, you should take oral medication to help your menstruation come quickly.