[Campbell Biology P.1087] A woman is prescribed a combination birth control pill containing s... | Practice Question

A woman is prescribed a combination birth control pill containing synthetic estrogen and progestin. Based on the information provided, what is the primary mechanism by which this pill prevents pregnancy?

  • A: It directly kills sperm in the vagina, preventing fertilization.
  • B: It blocks the transport of sperm through the male duct system.
  • C: It mimics negative feedback in the ovarian cycle, inhibiting the release of FSH and LH, thereby blocking ovulation and follicle development.
  • D: It physically blocks the union of sperm and egg in the oviduct.

Explanation

The text explains that 'hormonal contraceptives, most often in the form of birth control pills... mimic negative feedback in the ovarian cycle, stopping the release of GnRH by the hypothalamus and thus of FSH and LH by the pituitary. The prevention of LH release blocks ovulation. In addition, the inhibition of FSH secretion by the low dose of estrogens in the pills prevents follicles from developing.'