Contraception: Sorting the Evidence From the Noise
Effectiveness in practice differs substantially from effectiveness in perfect use, and the gap is largest for the methods people rely on most.
Key takeaways
- Most effective methods: implant, intrauterine device and intrauterine system
- Long-acting methods: do not depend on remembering anything
- Most useful single change: Ask specifically about long-acting methods, which are the most effective.
- Commonest mistake: Assuming a method works the same in real use as in perfect use.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
What it is
The range of methods used to prevent pregnancy, hormonal and non-hormonal. It sits within Womens Health. The table below gives the figures guidance actually works from.
The numbers, in one place
| Measure | Figure |
|---|---|
| Most effective methods | implant, intrauterine device and intrauterine system |
| Long-acting methods | do not depend on remembering anything |
| Emergency contraception | more effective the sooner it is taken |
| Copper IUD as emergency contraception | the most effective option, up to 5 days |
| Contraception after 40 | still needed until the menopause is confirmed |
What helps
The advice below comes straight from the guidance cited at the foot of this page.
- Ask specifically about long-acting methods, which are the most effective
- Get emergency contraception as early as possible; pharmacies supply it
- Review your method when your circumstances or medications change
- Continue contraception until advised it is no longer needed
What to avoid
What to steer clear of, and why it catches people out.
- Assuming a method works the same in real use as in perfect use
- Stopping contraception on the basis of irregular periods alone
- Combined hormonal methods without discussing migraine with aura, smoking over 35, or clot history
Where to go next
- Contraception: Just the Figures
- What Contraception Is, and Why It Matters
- Contraception — the reference entry
- Preconception Health: What the Evidence Actually Says
- Bone Health in Women: What the Evidence Actually Says
When to speak to a doctor
Seek urgent medical help for calf pain or swelling, chest pain, severe breathlessness, sudden severe headache, weakness on one side or vision loss while using combined hormonal contraception — these can indicate a clot or stroke. Tell your prescriber about migraine with aura, smoking over 35, high blood pressure or a history of clots.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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