Hormonal Contraception

Hormonal contraception delivers exogenous oestrogen and/or progestin to suppress ovulation, thicken cervical mucus and alter the endometrium. For NEET PG, the perennial favourites are the mechanism of the combined pill, the WHO MEC category 4 (absolute) contraindications, the Pearl index of each method, and the timing/choice of emergency contraception — almost every exam carries at least one single-best-answer from this cluster.

Classification

Hormonal methods are grouped by route, hormone content and duration of action.

Class	Examples	Hormones	Primary mechanism
Combined hormonal (CHC)	COC pill, transdermal patch (Evra), vaginal ring (NuvaRing)	Ethinyl-oestradiol + progestin	Ovulation suppression
Progestin-only pill (POP/minipill)	Desogestrel, norethisterone	Progestin only	Cervical mucus + variable ovulation block
Injectable	DMPA (Depo-Provera) 150 mg IM/104 mg SC; NET-EN	Progestin only	Ovulation suppression
Implant	Etonogestrel (Implanon/Nexplanon), Levonorgestrel (Jadelle)	Progestin only	Ovulation suppression
Hormonal IUS	Levonorgestrel-IUS (Mirena, 52 mg)	Progestin (local)	Endometrial atrophy + mucus
Emergency contraception	Levonorgestrel 1.5 mg, Ulipristal acetate 30 mg	Progestin / SPRM	Delay/inhibit ovulation

High-yield: The Pearl index = number of unintended pregnancies per 100 woman-years of use. Lower = more effective. Implants and LNG-IUS have the lowest typical-use failure (<1), while the male condom and natural methods have the highest.

The Pearl index — the most-tested numbers

Method	Perfect use	Typical use
Etonogestrel implant	0.05	0.05
LNG-IUS (Mirena)	0.2	0.2
DMPA injectable	0.2	4
Combined OCP	0.3	7–9
Progestin-only pill	0.3	7–9
Male condom	2	13–18
Withdrawal	4	20–22

High-yield: Implant is the single most effective reversible contraceptive (Pearl index ~0.05) — more effective than female sterilisation in some series. The wide perfect-vs-typical gap for DMPA and OCPs reflects compliance/late-dose dependence.

Mechanism of action

Combined oral contraceptive (COC):

1. Oestrogen (ethinyl-oestradiol) → suppresses FSH → prevents follicular development and selection of a dominant follicle; also stabilises the endometrium (cycle control).
2. Progestin → suppresses the LH surge → blocks ovulation (the principal contraceptive effect); thickens cervical mucus; renders endometrium thin/non-receptive; reduces tubal motility.

Stepwise (COC): EE suppresses FSH → no dominant follicle → progestin blocks LH surge → no ovulation → thick mucus + atrophic endometrium → contraception.

Progestin-only pill: Cervical mucus thickening is the dominant effect for older norethisterone POPs; desogestrel POP additionally inhibits ovulation in ~97% of cycles, making it more reliable. Endometrial thinning and reduced tubal transport contribute.

DMPA: High sustained progestin → consistent ovulation suppression (FSH/LH suppression) — this is why injectables, unlike old POPs, primarily work by blocking ovulation.

High-yield: The primary contraceptive action of the COC is ovulation inhibition via LH-surge suppression by the progestin component; oestrogen mainly contributes by suppressing FSH and providing cycle control.

How to start and the "7-day rule"

• COC started within the first 5 days of the menstrual cycle → immediately effective, no backup needed.
• Started later → use backup (condom/abstinence) for 7 days.
• POP (desogestrel) → backup for 48 hours (2 days) if started after day 5.
• DMPA → backup for 7 days if given after day 5.
• A missed COC (>24 h late, or ≥1 active pill missed): take the missed pill ASAP, continue the pack, use backup for 7 days; if missed in the last week of active pills, skip the hormone-free interval.

WHO Medical Eligibility Criteria (WHO MEC)

The WHO MEC stratifies conditions into 4 categories. Category 4 = absolute contraindication (unacceptable health risk).

Category	Meaning	Action
1	No restriction	Use freely
2	Advantages outweigh risks	Generally use
3	Risks usually outweigh advantages	Avoid unless no alternative
4	Unacceptable health risk	Do not use

Category 4 (absolute) contraindications to combined hormonal contraception

High-yield — memorise these COC "do-not-use" conditions:

• Migraine with aura (any age)
• History of / current venous thromboembolism (DVT/PE); known thrombogenic mutations (Factor V Leiden, prothrombin G20210A)
• Smoker ≥15 cigarettes/day and age ≥35 years
• Hypertension ≥160/100 mmHg, or HTN with vascular disease
• Current breast cancer
• Ischaemic heart disease, stroke, complicated valvular disease (pulmonary HTN, AF, endocarditis)
• <3 weeks postpartum (breastfeeding) — VTE risk; <21 days postpartum non-breastfeeding with risk factors
• Major surgery with prolonged immobilisation
• Severe (decompensated) cirrhosis, hepatocellular adenoma/carcinoma, active viral hepatitis
• Diabetes with nephropathy/retinopathy/neuropathy or >20 years' duration
• Systemic lupus with positive (or unknown) antiphospholipid antibodies

Mnemonic — "My CHA2 VeSSeL Breaks": Migraine with aura, Coronary/cerebrovascular disease, Hypertension ≥160/100, Age ≥35 + heavy smoking, VTE, Severe liver disease, Lupus (APLA+), Breast cancer.

High-yield: Migraine WITH aura and smoker ≥35 yrs ≥15/day are the two most repeated MCQ stems for COC contraindication. Migraine without aura is Category 2 (≥35 yrs) — usable with caution.

Progestin-only methods (POP, implant, DMPA, LNG-IUS) are largely free of oestrogen-related vascular risk, so they are the preferred choice when oestrogen is contraindicated — e.g. breastfeeding mothers, smokers >35, history of VTE, hypertension. Current breast cancer is Category 4 for all hormonal methods.

Specific methods — exam pearls

Combined OCP

• Standard monophasic pack: 21 active + 7 placebo (or 24/4). Withdrawal bleed occurs in the hormone-free week.
• Non-contraceptive benefits: ↓ risk of ovarian and endometrial carcinoma (protection persists years after stopping), ↓ benign breast disease, ↓ functional ovarian cysts, ↓ dysmenorrhoea/menorrhagia, ↓ ectopic pregnancy, regulation of cycles, treatment of PCOS/acne, ↓ colorectal cancer.
• Risks: VTE (relative risk ~2–4×, highest in first year and with higher-EE/newer progestins like desogestrel/drospirenone), small ↑ in cervical and breast cancer (the latter reverts ~10 yrs after stopping), hepatic adenoma, hypertension, MI/stroke in smokers >35.

High-yield: COCs reduce ovarian and endometrial cancer but cause a small increase in cervical and breast cancer — a classic two-part MCQ.

Progestin-only pill (minipill)

• Best for breastfeeding women, smokers >35, oestrogen-contraindicated patients.
• Must be taken at the same time daily — old POPs lose efficacy if >3 h late (desogestrel allows a 12-h window).
• Side effect: irregular bleeding/spotting (commonest reason for discontinuation).

DMPA (Depo-Provera)

• 150 mg IM every 12–13 weeks.
• Delayed return of fertility — mean ~9 months after the last injection (a tested distinguishing fact).
• Reversible loss of bone mineral density (BMD) → black-box caution; reversible on stopping. Useful in sickle cell disease (reduces crises) and seizure disorders.
• Causes amenorrhoea in ~50% by 1 year (a benefit in menorrhagia).
• Weight gain is the typical metabolic concern.

High-yield: DMPA → delayed return of fertility (~9 months) and reversible reduction in BMD. It is the only common method where return of fertility is significantly delayed.

Implant (etonogestrel — Implanon/Nexplanon)

• Single subdermal rod, effective for 3 years, Pearl index ~0.05. Rapid return of fertility on removal. Irregular bleeding is the main side effect/discontinuation reason.

LNG-IUS (Mirena)

• Local progestin → endometrial atrophy; lasts ~5 years (now licensed up to 8). First-line for heavy menstrual bleeding; provides endometrial protection in HRT. Reduces ectopic risk overall but, if pregnancy occurs, a higher proportion are ectopic.

Emergency contraception (EC) — high-yield timing

Method	Window	Mechanism	Notes
Levonorgestrel 1.5 mg	within 72 h (up to 120 h, declining efficacy)	Delays/inhibits ovulation	OTC; less effective if BMI >26/weight >70 kg; least effective EC
Ulipristal acetate 30 mg	within 120 h (5 days)	Selective progesterone receptor modulator (SPRM); delays ovulation even after LH rise begun	More effective than LNG, esp. days 3–5 and higher BMI
Copper IUD	within 120 h (5 days) of unprotected sex (or 5 days post earliest ovulation)	Spermicidal/anti-implantation	Most effective EC (>99%); provides ongoing contraception

High-yield: The copper IUD is the most effective emergency contraceptive. Among pills, ulipristal > levonorgestrel, and ulipristal retains efficacy through day 5. LNG EC works only if given before ovulation — it does not disrupt an established pregnancy and is not an abortifacient.

High-yield: Do not give ulipristal and levonorgestrel together — both act on the progesterone receptor and LNG (a progestin) blunts ulipristal's SPRM effect. Quick-starting hormonal contraception after ulipristal should be delayed 5 days (LNG-progestin can attenuate it); after LNG-EC, hormonal contraception can be started immediately with backup.

EC stepwise approach: Unprotected intercourse → assess time elapsed → ≤120 h & wants ongoing contraception or maximum efficacy → Cu-IUD → if pills: ≤120 h → ulipristal 30 mg (preferred, esp. >72 h or high BMI) → if ulipristal unavailable/recent progestin use → LNG 1.5 mg if ≤72 h → arrange ongoing contraception + pregnancy test if next period delayed >1 week.

The older Yuzpe regimen (combined EE + LNG) is obsolete (more nausea, less effective) but still appears in MCQs as a historical EC method.

Drug interactions

• Enzyme inducers reduce efficacy of oestrogen/progestin: rifampicin/rifabutin (most important), carbamazepine, phenytoin, phenobarbitone, topiramate, St John's wort, some antiretrovirals. → Advise an alternative (Cu-IUD/DMPA) or additional method.
• Lamotrigine levels are lowered by COCs (loss of seizure control) — bidirectional caution.
• Broad-spectrum antibiotics (amoxicillin etc.) do not meaningfully reduce COC efficacy (myth) — only enzyme-inducing antimicrobials matter.

High-yield: Rifampicin is the classic enzyme inducer that causes COC/POP failure → use DMPA or Cu-IUD instead.

Complications & warning signs (ACHES)

ACHES mnemonic for serious COC warning symptoms → stop pill and evaluate:

• A — Abdominal pain (hepatic/mesenteric thrombosis)
• C — Chest pain/dyspnoea (PE/MI)
• H — Headache, severe (stroke, new aura)
• E — Eye problems / visual loss (retinal vein thrombosis)
• S — Severe leg pain/swelling (DVT)

Key differentials / "which method?" scenarios

• Breastfeeding (<6 weeks postpartum): avoid CHC (Cat 4); use POP, implant, DMPA or LAM.
• Smoker >35, ≥15/day: CHC contraindicated → progestin-only or Cu-IUD.
• History of DVT/PE or thrombophilia: avoid CHC → progestin-only / Cu-IUD.
• Heavy menstrual bleeding wanting contraception: LNG-IUS first line.
• Wants most effective reversible method: implant or LNG-IUS (LARC).
• Needs ongoing + emergency cover, presents <5 days: Copper IUD.
• PCOS with hirsutism/acne (no contraindication): COC with anti-androgenic progestin (e.g., drospirenone/cyproterone).

Recently asked / exam angle

• Mechanism of COC — the single best answer is suppression of the LH surge / inhibition of ovulation (progestin), with FSH suppression by oestrogen. Distractor: "thickening of cervical mucus" is the POP/minipill dominant mechanism.
• Category 4 WHO MEC for COC — repeated stems: migraine with aura, smoker ≥35 + ≥15/day, prior VTE, BP ≥160/100, current breast cancer, <3 weeks postpartum breastfeeding.
• Pearl index ranking — implant (lowest) vs OCP vs condom (highest among listed); definition "per 100 woman-years."
• Emergency contraception — most effective = copper IUD; ulipristal window = 5 days; LNG window = 72 h; do not combine ulipristal + LNG.
• DMPA — delayed fertility (~9 months) and reversible BMD loss.
• Non-contraceptive benefit — COC protects against ovarian and endometrial cancer.
• Enzyme inducer causing failure — rifampicin.
• POP of choice in lactation and oestrogen-contraindicated states.

Rapid revision

1. Pearl index = unintended pregnancies per 100 woman-years; lower = better.
2. COC's main action = progestin suppresses LH surge → no ovulation; oestrogen suppresses FSH + gives cycle control.
3. Migraine with aura and smoker ≥35 yrs ≥15/day = absolute (Cat 4) contraindications to COC.
4. WHO MEC Category 4 = unacceptable risk = do not use.
5. COC reduces ovarian + endometrial cancer; small increase in cervical + breast cancer (breast risk reverts ~10 yrs after stopping).
6. Implant = most effective reversible method (Pearl ~0.05).
7. DMPA: q12–13 weekly, delayed fertility ~9 months, reversible BMD loss, helps sickle cell.
8. POP/desogestrel = choice in lactation and oestrogen-contraindicated women; main side effect = irregular bleeding.
9. Copper IUD = most effective emergency contraceptive; insert within 5 days.
10. EC pills: ulipristal (SPRM) ≤120 h > levonorgestrel ≤72 h; never combine the two.
11. Rifampicin (enzyme inducer) → COC/POP failure → switch to DMPA/Cu-IUD.
12. LNG-IUS (Mirena) = first-line for heavy menstrual bleeding; ACHES = COC danger signs.