Everything You Need to Know About Contraception methods for Step 1

Contraception is one of those Step 1 topics that feels “obvious”… until a question asks which method increases thrombosis risk, which is safe postpartum, or why rifampin makes pills fail. The trick is to organize contraception by mechanism + estrogen exposure + timing—then layer in the high-yield adverse effects, contraindications, and classic USMLE associations.

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Big-Picture Definition (What “Contraception” Is Actually Doing)

Contraception prevents pregnancy by interfering with one (or more) of the following:

• Ovulation (suppress LH surge)
• Fertilization (block sperm transport or function)
• Implantation (alter endometrium; primarily via progestin effects)

Key physiology anchor: The LH surge triggers ovulation. Many hormonal methods work by preventing that surge.

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Core Pathophysiology & Mechanisms (Step 1-Friendly)

Estrogen + Progestin: what each component does

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Why progestin-only works even without fully blocking ovulation: cervical mucus thickening is a powerful barrier.

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The Step 1 Classification System (Learn It Once)

1) Combined Hormonal Contraceptives (CHCs): estrogen + progestin

Includes:

• Combined oral contraceptive pills (OCPs)
• Transdermal patch
• Vaginal ring

Mechanism

• Estrogen suppresses FSH
• Progestin suppresses LH surge + thickens cervical mucus

High-yield benefits

• ↓ risk of endometrial cancer and ovarian cancer
• Improves dysmenorrhea, menorrhagia, acne
• Helpful in PCOS (cycle control, lower androgens)

High-yield adverse effects / risks

• Thrombosis (DVT/PE), especially with additional risk factors
• Hypertension
• Cholestasis
• Hepatic adenoma (rare but classic)
• Nausea, breast tenderness, headache
• Can worsen migraine with aura risk profile (contraindication)

Contraindications (USMLE loves these) Remember: avoid estrogen when clot/stroke risk is high.

• Age > 35 + smoking
• History of DVT/PE or known thrombophilia
• Migraine with aura
• Uncontrolled HTN
• Breast cancer (hormone-sensitive)
• Active liver disease (e.g., severe cirrhosis, hepatic tumors)
• Postpartum early period (hypercoagulable state; more below)

Drug interactions

• Enzyme inducers ↓ effectiveness:
  • Rifampin/rifabutin
  • Many anti-seizure meds (e.g., carbamazepine, phenytoin, phenobarbital, topiramate in higher doses)
  • St. John’s wort (less tested but commonly referenced)

Clinical vignette tip

• “Woman on OCPs treated with rifampin becomes pregnant” → classic.

First Aid cross-reference

• First Aid (Repro/Endocrine sections): Combined OCP adverse effects (thromboembolism, hepatic adenoma) and contraindications (smoker >35, migraine with aura).

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2) Progestin-Only Methods (no estrogen)

Includes:

• Progestin-only pill (“mini-pill”)
• Depot medroxyprogesterone acetate (DMPA) injection
• Etonogestrel implant
• Levonorgestrel (LNG) IUD

Shared mechanism

• Thickens cervical mucus
• Thins endometrium
• Variable ovulation suppression (stronger with DMPA/implant)

Progestin-only pill

• Must be taken same time daily (short window); otherwise higher failure than long-acting methods.
• Great when estrogen is contraindicated.

DMPA (Depo shot)

High-yield associations

• ↓ bone mineral density (reversible)
• Weight gain
• Delayed return to fertility after stopping (can take months)
• Can reduce seizure frequency in some (less commonly tested)

Implant (etonogestrel)

• Long-acting, very effective
• Common AE: irregular bleeding

LNG IUD

• Progestin locally → markedly decreases menstrual bleeding
• Great for heavy menstrual bleeding
• Can cause amenorrhea over time

Why progestin-only is high-yield postpartum

• Safe in breastfeeding and when avoiding estrogen-related thrombosis risk.

First Aid cross-reference

• First Aid: DMPA → decreased bone density, progestin IUD → decreased bleeding/amenorrhea.

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3) Intrauterine Devices (IUDs): Copper vs Levonorgestrel

IUD complications (testable)

• Uterine perforation (rare)
• Expulsion (esp. soon after insertion)
• Pelvic inflammatory disease (PID) risk is mainly in the first ~20 days after insertion if an STI is present at insertion
• If pregnancy occurs with an IUD in place → higher risk ectopic pregnancy proportionally (overall pregnancy risk is still very low)

Who should not get an IUD?

• Active PID or untreated cervicitis (e.g., gonorrhea/chlamydia)
• Distorted uterine cavity (relative, depends on scenario)

First Aid cross-reference

• First Aid: Copper IUD: emergency contraception; increased bleeding, LNG IUD: decreased bleeding, and PID risk near insertion if infected.

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4) Barrier Methods (mechanical + behavior)

Includes:

• Male condoms
• Female condoms
• Diaphragm + spermicide
• Cervical cap
• Sponge

High-yield points

• Condoms reduce STI transmission (biggest exam point)
• Diaphragm + spermicide: increased risk of UTIs (often due to urinary retention + altered flora)
  • Think: “recurrent UTIs after new diaphragm use.”
• Latex allergy scenarios: consider non-latex alternatives.

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5) Fertility Awareness + Withdrawal (less reliable)

• Requires predictable cycles and strong adherence.
• Step-wise, more likely to be tested as “least effective typical use.”

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6) Permanent Sterilization

• Tubal ligation (female)
• Vasectomy (male)

High-yield

• Vasectomy: sperm may persist for weeks → need semen analysis confirmation.
• “Failure after tubal ligation” raises concern for ectopic pregnancy.

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Emergency Contraception (Must-Know Table)

Common USMLE trap

• Emergency contraception does not disrupt an implanted pregnancy (it prevents/delays ovulation or fertilization).

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Clinical Presentation (How It Shows Up on Exams)

Most contraception questions are not “patient has contraception side effects, diagnose contraception.” They’re more like:

• Picking the best method given comorbidities (e.g., smoker >35, migraines with aura, postpartum)
• Identifying adverse effect (e.g., DMPA → bone loss; copper IUD → heavier menses)
• Identifying drug interaction (rifampin → OCP failure)
• Choosing emergency contraception option and timing

Classic side-effect patterns

• CHC: nausea, breast tenderness, breakthrough bleeding, VTE risk
• Progestin-only: irregular bleeding, mood changes
• DMPA: weight gain, delayed fertility return, ↓ bone density
• Copper IUD: heavier/longer periods, cramps
• LNG IUD: decreased bleeding/amenorrhea

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Diagnosis (What Are You “Diagnosing,” Exactly?)

Usually you’re not diagnosing the contraception method; you’re diagnosing:

1. A contraindication to estrogen:

   • Migraine with aura
   • Smoking + age > 35
   • Prior VTE / thrombophilia
   • Uncontrolled HTN

2. A complication:

   • Concern for ectopic pregnancy (esp. pelvic pain + bleeding + pregnancy risk factors)
   • PID after insertion with fever, pelvic pain, cervical motion tenderness
   • Hepatic adenoma with RUQ pain + estrogen exposure history

3. Pregnancy when missed periods / symptoms occur:

   • Always check a pregnancy test first in relevant vignettes.

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Treatment & Counseling (What Step 1/2 Wants You to Choose)

Choosing a method: quick high-yield algorithm

If estrogen is contraindicated → choose progestin-only or non-hormonal:

• LNG IUD, copper IUD, implant, DMPA, mini-pill, condoms

If patient has heavy menstrual bleeding:

• Levonorgestrel IUD (often best)
• CHCs can also help

If patient wants best efficacy with minimal user error:

• LARC methods:
  • Implant
  • IUDs (copper or LNG)

If patient needs STI protection:

• Condoms (alone or dual-method with another contraceptive)

Postpartum & breastfeeding (frequent NBME-style)

• Immediate postpartum is hypercoagulable; avoid estrogen early postpartum.
• Progestin-only methods and IUDs are commonly used options postpartum; condoms always OK.
• Step framing: “Breastfeeding mother wants contraception” → pick progestin-only or IUD.

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High-Yield Associations & Buzzwords (Rapid Review)

Estrogen-related

• ↑ clotting factors → DVT/PE risk
• Migraines with aura → avoid estrogen
• Smoker >35 → avoid estrogen
• Hepatic adenoma association

Progestin-related

• Irregular bleeding
• Thick cervical mucus
• DMPA → ↓ bone density, weight gain, delayed fertility return

IUD-related

• Copper: heavier menses; emergency contraception
• LNG: lighter menses/amenorrhea
• PID risk highest shortly after insertion if STI present
• Pregnancy with IUD → consider ectopic (relative risk)

Enzyme-inducer interactions

• Rifampin (classic)
• Some anti-epileptics

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Mini Table: “Which One Is It?” (Fast Exam Discriminators)

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First Aid Cross-References (Where This Lives Conceptually)

While page numbers vary by edition, these topics are consistently covered in First Aid under:

• Reproductive Endocrinology: hypothalamic-pituitary-ovarian axis (LH surge/ovulation)
• Pharmacology—Reproductive: OCPs (combined vs progestin-only), AEs/contraindications
• Obstetrics/Gynecology high-yield facts: IUD types and effects, emergency contraception

Use First Aid to lock in:

• Combined OCP contraindications (smoker >35, migraine with aura, VTE)
• DMPA → decreased bone density
• Copper vs LNG IUD bleeding patterns
• Rifampin → decreased OCP efficacy

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USMLE-Style Checkpoints (If You Can Answer These, You’re Solid)

1. Why do CHCs increase thrombosis risk?

   • Estrogen increases hepatic production of clotting factors → hypercoagulability.

2. Which method is most effective emergency contraception?

   • Copper IUD.

3. Which method commonly decreases bleeding/causes amenorrhea?

   • Levonorgestrel IUD (also CHCs can decrease bleeding, but LNG IUD is the standout).

4. Which method decreases bone mineral density?

   • DMPA.

5. Which medication classically reduces OCP efficacy?

   • Rifampin (CYP induction).