Emergency contraceptive pill (Levonorgestrel 1.5 mg) is most effective if taken within 72 hours of unprotected intercourse. Its primary mechanism of action is:

• A Preventing implantation of a fertilized ovum (abortifacient effect)
• B Delaying or inhibiting ovulation, primarily through LH surge suppression ✓
• C Thickening of cervical mucus to prevent sperm penetration (primary mechanism)
• D Inducing premature luteolysis and progesterone withdrawal

Explanation

Levonorgestrel emergency contraception works primarily by delaying or inhibiting ovulation through suppression of the LH surge. It does NOT interrupt an established pregnancy and is not an abortifacient. When taken before the LH surge, it delays ovulation so that sperm are no longer viable when the egg is released. If ovulation has already occurred, levonorgestrel has minimal or no effect on fertilization or implantation. Cervical mucus thickening is a minor secondary mechanism. Luteolysis mechanism pertains to mifepristone.

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.