What does an emergency contraceptive pill aim to prevent?

An emergency contraceptive pill primarily aims to prevent the fertilization of an egg by sperm. These pills contain hormones that work to stop sperm from fertilizing an egg, which can help to prevent an unintended pregnancy after unprotected sex or contraceptive failure.

When taken within a specific timeframe after unprotected intercourse, these pills can alter the hormonal balance in the body, thereby inhibiting or delaying ovulation and affecting the reproductive process. However, their core function is fundamentally linked to stopping the fertilization process itself. This is why the choice emphasizing fertilization is the correct answer.

The other options do not accurately represent the primary function of emergency contraceptive pills. For example, while these pills may indirectly influence ovulation, their main action is not directly aimed at preventing ovulation itself. Additionally, they do not prevent the transmission of sexually transmitted infections (STIs) nor do they cause any effects on an already developing fetus, which distinguishes their purpose from those options.