A 30-year-old woman initiates combined oral contraceptive pill (COCP). Which mechanism is responsible for the PRIMARY contraceptive action of combined oral contraceptives?

• A Endometrial atrophy preventing implantation
• B Inhibition of ovulation by suppression of FSH and LH via negative feedback on the hypothalamo-pituitary axis ✓
• C Cervical mucus thickening preventing sperm penetration
• D Inhibition of sperm capacitation in the uterine cavity

Explanation

The primary mechanism of action of the combined oral contraceptive pill is suppression of ovulation through inhibition of the hypothalamo-pituitary-ovarian axis: the progestogen component primarily suppresses the LH surge (preventing ovulation), while the oestrogen component suppresses FSH (inhibiting follicular development). Secondary mechanisms include cervical mucus thickening (progestogen-mediated), endometrial thinning, and impaired tubal motility. Endometrial atrophy and cervical mucus effects are backup mechanisms, important especially in progestogen-only contraceptives.

Reference: Shaw's Textbook of Gynaecology, 17th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.