Contraceptive method mechanisms, effectiveness, and contraindications tested on USMLE Step 1.
35 cards · basic cards · AI-written, checked twice. Edit anything.
- By what mechanism do combined oral contraceptives (estrogen + progestin) prevent pregnancy?
- They suppress GnRH pulsatility, lowering FSH and LH so the LH surge and ovulation never occur.
- Which hormone in combined OCPs is mainly responsible for thickening cervical mucus?
- The progestin component.
- What is the perfect-use failure rate of combined oral contraceptives?
- About 0.3% per year.
- What is the typical-use failure rate of combined oral contraceptives?
- About 7% per year.
- What is the mechanism of action of the copper IUD?
- Copper ions trigger a sterile inflammatory reaction that is toxic to sperm and ova, with no hormonal effect.
- How long is the copper IUD effective for pregnancy prevention?
- Up to 10 years.
- What is the mechanism of action of the levonorgestrel-releasing IUD?
- It thickens cervical mucus and thins the endometrial lining, and can also suppress ovulation in some cycles.
- Which category of reversible contraception has the lowest typical-use failure rate?
- Long-acting reversible contraception (LARC): IUDs and the subdermal implant.
- What is the mechanism of action of depot medroxyprogesterone acetate (DMPA)?
- It suppresses the LH surge, inhibiting ovulation.
- What is a major long-term side effect of DMPA (Depo-Provera)?
- Decreased bone mineral density.
- How often must DMPA be injected to maintain contraceptive effectiveness?
- Every 3 months (about every 12 weeks).
- How long does a single etonogestrel subdermal implant (Nexplanon) provide contraception?
- Up to 3 years.
- Why are estrogen-containing contraceptives contraindicated in smokers over age 35?
- Increased risk of venous thromboembolism, myocardial infarction, and stroke.
- Why is migraine with aura an absolute contraindication to estrogen-containing contraceptives?
- It increases the risk of ischemic stroke.
- Why is a history of venous thromboembolism a contraindication to estrogen-containing contraceptives?
- Estrogen increases clotting factors, raising the risk of recurrent VTE.