Levonorgestrel, the main active ingredient of the I-Pill, is a synthetic version of the naturally occurring female sex hormone, progesterone. During a regular menstrual cycle, a mature egg is released from the ovaries, in a process called ovulation.
Oral emergency contraception works by postponing this ovulation process. I-Pill prevents pregnancy by temporarily halting the production of eggs, blocking fertilization, or preventing a fertilized egg from getting implanted in the uterus.