What is the action of progestin in emergency contraception like levonorgestrel?

Progestin, such as levonorgestrel, primarily acts by inhibiting ovulation, which is the primary mechanism through which emergency contraception operates. By preventing or delaying the release of an egg from the ovary, progestins effectively reduce the chance of fertilization occurring if unprotected intercourse has taken place.

In the context of emergency contraception, the timing of administration is crucial; when taken before ovulation, it can prevent the ovulatory process from occurring, thereby reducing the likelihood of a pregnancy. Additionally, progestins may alter the endometrial lining, making implantation of a fertilized egg less likely if ovulation has already occurred, but this is not the primary action.

Understanding this mechanism is vital for recognizing how emergency contraception works and its role in reproductive health. The other options presented do not align with the function of progestins in emergency contraception, as they either suggest processes that are not relevant in this context or involve actions that are contrary to the purpose of levonorgestrel in preventing unintended pregnancies.