What role do intrauterine devices (IUDs) play in contraception?

Intrauterine devices (IUDs) serve as a form of contraception by preventing both fertilization and implantation. The presence of an IUD in the uterus creates an environment that is inhospitable to sperm, thereby reducing the likelihood of sperm successfully fertilizing an egg. Additionally, if fertilization were to occur, the IUD alters the uterine lining so that it is less receptive to a fertilized egg, effectively preventing implantation.

This unique dual mechanism is what makes IUDs effective as contraceptive devices. They are designed to remain in place in the uterus for an extended period, providing long-term contraception without the need for daily attention, unlike some other methods.