Emergency contraceptive pills (ECPs) with levonorgestrel 1.5 mg are recommended to be taken within 72 hours of unprotected intercourse. Their primary mechanism of action is:

• A Prevention of fertilization by thickening cervical mucus
• B Interference with implantation of a fertilized ovum
• C Luteolysis and progesterone withdrawal causing endometrial shedding
• D Inhibition or delay of ovulation ✓

Explanation

The primary and predominant mechanism of levonorgestrel emergency contraception is inhibition or delay of ovulation (when taken before the LH surge). It is ineffective if ovulation has already occurred. It does not consistently prevent fertilization or implantation of a fertilized ovum at the doses used, distinguishing it from mifepristone (abortifacient). Cervical mucus thickening contributes minimally to its contraceptive effect when given as a single post-coital dose. This mechanism clarification is important for counselling and is distinct from the mechanism of ongoing progestin-only pills.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.