Contraceptive failure among women using combined oral contraceptive pills (COCPs) most commonly occurs due to:
- A Development of acquired resistance to estrogen over time
- B Changes in liver metabolism leading to decreased drug levels with age
- C Inconsistent or incorrect use (user failure), especially missing pills in the first or third week ✓
- D Autoimmune destruction of hypothalamic-pituitary axis
Correct answer: C. Inconsistent or incorrect use (user failure), especially missing pills in the first or third week
Explanation
The most common cause of COCP failure is user error — particularly missing pills, especially during the first week (when ovulation suppression is critical), the third week (when pill-free interval effectively begins early), or when restarting after a missed cycle. Drug interactions (rifampicin, anticonvulsants inducing CYP450) also reduce efficacy. Perfect-use failure rate is 0.3% versus typical-use 7% per year.
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.