Which class of drugs is used to prevent pregnancy by suppressing ovulation?

The correct choice involves oral contraceptives, which are specifically designed to prevent pregnancy primarily by suppressing ovulation. These medications contain hormones, such as estrogen and progestin, which work by inhibiting the release of eggs from the ovaries. When ovulation does not occur, the likelihood of fertilization and subsequent pregnancy is greatly reduced.

Oral contraceptives also alter the cervical mucus, making it thicker and more difficult for sperm to enter the uterus, and change the endometrial lining, minimizing the chances of implantation should fertilization occur. This comprehensive action on the reproductive system is key to their effectiveness as a contraceptive method.

Other classes of drugs mentioned do not serve this purpose. Anticoagulants, for example, are used to prevent blood clots; fibrinolytics are aimed at breaking down clots that have formed; and antihyperlipidemics are used to lower lipid levels in the blood. None of these classes influence ovulation or directly prevent pregnancy. Thus, the unique role of oral contraceptives in suppressing ovulation underscores their position as the correct answer.