Contraception - progestogen-only methods
Exam Tips
- Differentiate POP types: traditional POPs mainly alter cervical mucus and have stricter timing sensitivity; desogestrel/drospirenone suppress ovulation more reliably.
- Memorise UK doses and durations: etonogestrel implant 68 mg for 3 years; DMPA 150 mg IM or 104 mg SC every 13 weeks; NET-EN 200 mg every 8 weeks.
- Starting windows are high yield: day 1 (drospirenone) or days 1-5 (other POPs) gives immediate cover; otherwise add 7 days (drospirenone) or 2 days (other POPs) barrier protection.
- After ulipristal emergency contraception, delay POP quick start by 5 days and arrange pregnancy test ≥3 weeks after last UPSI.
- Know key safety red flags: drospirenone and renal impairment/hyperkalaemia risk; DMPA and bone mineral density plus delayed fertility return.
- For visual revision, use a contraception mechanism diagram showing HPO-axis suppression vs cervical mucus effects across POP, implant, and injectables (see figure in your core reproductive endocrinology chapter).
Definition
Progestogen-only contraception comprises oral pills, a subdermal implant, and injectable depot preparations used to prevent pregnancy without oestrogen exposure. In UK practice, these methods are key options when combined hormonal contraception is unsuitable (for example during breastfeeding or with oestrogen-related risk), and their effectiveness depends on method type, adherence, and interacting medicines.
Pathophysiology
Progestogen-only methods act at multiple reproductive targets. Desogestrel 75 micrograms and drospirenone 4 mg POPs suppress ovulation more consistently via anti-gonadotrophic effects, while traditional POPs (norethisterone 350 micrograms, levonorgestrel 30 micrograms) rely more on rapid but short-lived cervical mucus thickening, endometrial thinning, and altered tubal ciliary/motility function, so strict daily timing is critical. The etonogestrel implant (68 mg) produces sustained systemic progestogen levels and usually inhibits ovulation within about 24 hours of insertion, with additional mucus effects. Injectable depot progestogens (DMPA 150 mg IM, DMPA 104 mg SC, NET-EN 200 mg) suppress ovulation, thicken cervical mucus, and induce endometrial changes that reduce implantation likelihood.
Risk Factors
- Incorrect or inconsistent POP use (especially timing errors with traditional POPs)
- Use of liver enzyme-inducing drugs reducing efficacy of POPs and implant (for example rifampicin, enzyme-inducing antiepileptics, St John’s wort)
- Severe renal insufficiency or acute renal failure (contraindication to drospirenone POP)
- Hyperkalaemia risk states or potassium-raising therapy when considering drospirenone (for example potassium-sparing diuretics, aldosterone antagonists, potassium supplements)
- Risk factors for low bone mineral density when using DMPA long term
- High baseline concern about delayed fertility return (relevant for injectable choice)
Clinical Features
Symptoms
- Unscheduled bleeding/spotting (common early with all progestogen-only methods)
- Amenorrhoea over time (particularly with injectables)
- Breast tenderness
- Headache or mood change
- Weight gain (more commonly reported with DMPA)
- Possible improvement in dysmenorrhoea/endometriosis-associated pain in some users
Signs
- Usually normal general examination
- Implant insertion/removal site bruising, tenderness, or local complications
- Injection-site discomfort with depot methods
- Blood pressure and hydration/renal assessment may be relevant when prescribing drospirenone in higher-risk patients
Investigations
Management
Lifestyle Modifications
- Shared decision-making on method choice (daily pill vs long-acting reversible options) based on adherence, bleeding expectations, and fertility plans
- Advise condoms for STI prevention because progestogen-only methods do not protect against STIs
- When starting outside immediate effective window, use additional contraception: 2 days for most POPs, 7 days for drospirenone POP
- If quick-starting after ulipristal acetate emergency contraception, delay POP start for 5 days and use barrier precautions
- Counsel on expected irregular bleeding and when to seek review (persistent heavy bleeding, pain, pregnancy symptoms, STI risk)
Pharmacological Treatment
Progestogen-only pills (oral)
- Norethisterone 350 micrograms once daily (Noriday)
- Levonorgestrel 30 micrograms once daily (Norgeston)
- Desogestrel 75 micrograms once daily (for example Cerazette/Cerelle)
- Drospirenone 4 mg once daily in a 24 active/4 inert cycle (Slynd)
Initiate day 1 (drospirenone) or days 1-5 (other POPs) with immediate protection; otherwise start if reasonably not pregnant and add condoms/abstinence for 7 days (drospirenone) or 2 days (others). Contraindications/safety: drospirenone is contraindicated in severe renal insufficiency/acute renal failure; avoid in known hyperkalaemia or untreated hypoaldosteronism; check interactions with potassium-raising drugs.
Subdermal progestogen implant
- Etonogestrel 68 mg subdermal implant, effective for 3 years (Nexplanon)
Very high efficacy and rapid return of fertility after removal. Insertion/removal requires trained clinician and local anaesthetic technique. Efficacy can be reduced by enzyme-inducing drugs; consider alternative method where interaction risk persists.
Injectable depot progestogens
- Medroxyprogesterone acetate 150 mg IM every 13 weeks (Depo-Provera)
- Medroxyprogesterone acetate 104 mg SC every 13 weeks (Sayana Press)
- Norethisterone enantate 200 mg IM every 8 weeks (Noristerat, less commonly used)
Useful when adherence to daily pills is difficult and not significantly affected by enzyme inducers. Safety counselling: delayed return to fertility (can be up to around 1 year), weight gain, and reversible reduction in bone mineral density; reassess risks/benefits in those with osteoporosis risk.
Surgical / Interventional
- Subdermal implant insertion and removal under local anaesthetic by a trained practitioner
Complications
- Unintended pregnancy (including from user error or drug interactions)
- Problematic unscheduled bleeding leading to discontinuation
- DMPA-associated weight gain
- Reversible reduction in bone mineral density with prolonged injectable use
- Delay in return of fertility after stopping injectables
- Implant procedural complications (difficult removal, local neurovascular injury, migration - rare)
Prognosis
Overall prognosis is excellent when the method matches patient priorities and is used correctly: implant and injectables are highly effective with low failure rates, while POP effectiveness in real-world use is limited mainly by adherence. Fertility usually returns quickly after stopping POP or removing implant, but may be delayed for months after depot injections. Bleeding irregularities are common early and often settle, and continuation improves with anticipatory counselling.
Sources & References
✅NICE Guidelines(1)
- Contraception - progestogen-only methods[overview]