In addition to inhibiting ovulation, how do combined contraceptives further prevent pregnancy?

• A. Creating a toxic environment for sperm
• B. Decreasing production of sex hormone-binding globulin
• C. Thinning the uterine wall
• D. Increasing the viscosity of cervical mucus

Answer: (D)

Combined contraceptives play a multifaceted role in preventing pregnancy, and one of the mechanisms by which they achieve this is by increasing the viscosity of cervical mucus. The hormones present in these contraceptives, typically estrogen and progestin, alter the properties of the cervical mucus, making it thicker and less permeable to sperm. This thickening creates a barrier that makes it more challenging for sperm to travel through the cervical canal and reach the egg, thereby contributing to the overall contraceptive effect.

In contrast, while options such as thinning the uterine wall may suggest alterations to the endometrium, and creating a toxic environment for sperm relates to how sperm function could be inhibited, it’s the viscosity of cervical mucus that provides a direct mechanical barrier against sperm entry. This combination of actions—suppressing ovulation and affecting cervical mucus—enhances the effectiveness of combined contraceptives in preventing pregnancy. Additionally, the decrease in hormone-binding globulin is less relevant to the immediate preventive measures against conception but rather influences the bioavailability of circulating hormones.