Questions: Current Attempt in Progress Combined oral contraceptives decrease the likelihood of pregnancy by suppressing FSH and LH. preventing development of a dominant follicle in the ovary. blocking implantation in the uterus. inhibiting transport of ova and sperm in the uterine tubes. all of these choices. eTextbook and Media Save for Later

The answer is the first one: suppressing FSH and LH.

Explanation for each option:

1. Suppressing FSH and LH: Correct. Combined oral contraceptives contain estrogen and progestin, which work by suppressing the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary gland. This suppression prevents ovulation, which is the release of an egg from the ovary.

2. Preventing development of a dominant follicle in the ovary: Correct. By suppressing FSH, combined oral contraceptives prevent the development of a dominant follicle, which is necessary for ovulation.

3. Blocking implantation in the uterus: Partially correct. While combined oral contraceptives primarily work by preventing ovulation, they also alter the endometrial lining, making it less suitable for implantation. However, this is not their primary mechanism of action.

4. Inhibiting transport of ova and sperm in the uterine tubes: Partially correct. Combined oral contraceptives can thicken cervical mucus, which inhibits sperm transport. However, this is also not their primary mechanism of action.

5. All of these choices: Incorrect. While combined oral contraceptives have multiple effects, their primary and most significant mechanism is the suppression of FSH and LH to prevent ovulation.

Summary: Combined oral contraceptives primarily decrease the likelihood of pregnancy by suppressing FSH and LH, which prevents ovulation. Other effects, such as altering the endometrial lining and thickening cervical mucus, also contribute but are secondary mechanisms.