What is CHC?
CHC = Combined Hormonal Contraception — the pill (oestrogen + progestogen), the vaginal ring and the hormone patch. Highly effective, but carrying a higher risk of thrombosis than hormone-free methods.
WHO MEC categories
The World Health Organization (WHO) classifies the medical eligibility of a contraceptive method into four categories:
- 1 – no restriction
- 2 – advantages generally outweigh the risks
- 3 – risks generally outweigh the advantages; consider only if more appropriate methods are unavailable or unacceptable and careful specialist assessment is possible
- 4 – do not use because the method represents an unacceptable health risk
The category may differ between starting (S) and continuing (C) a method. The table below applies to the combined pill, patch and vaginal ring under WHO MEC, 6th edition (2025); it is not a self-diagnosis tool.
Complete overview of WHO MEC 3/4 situations for CHC
| Situation | WHO MEC | Interpretation |
|---|---|---|
| Breastfeeding < 6 weeks after birth | 4 | Do not use CHC |
| Primarily breastfeeding from 6 weeks to < 6 months after birth | 3 | Generally do not use |
| Not breastfeeding, < 21 days after birth | 3 without additional VTE risk factors; 4 with additional VTE risk factors | VTE risk factors include previous VTE, thrombophilia, immobility, transfusion at delivery, BMI ≥ 30, postpartum haemorrhage, pre-eclampsia or smoking |
| Not breastfeeding, 21–42 days after birth | 3 with additional VTE risk factors | Without additional VTE risk factors MEC 2; after 42 days MEC 1 |
| Smoking from age 35 | 3 for < 15 cigarettes/day; 4 for ≥ 15/day | Age and number smoked must be assessed together |
| Multiple major risk factors for arterial cardiovascular disease (e.g. older age, smoking, diabetes, hypertension and known dyslipidaemia) | 3/4 | Depends on the type, number and severity of the factors |
| History of hypertension where BP cannot currently be assessed; adequately controlled hypertension; or BP 140–159/90–99 mmHg | 3 | A single reading is not sufficient to diagnose hypertension |
| BP ≥ 160 systolic or ≥ 100 diastolic; or vascular disease | 4 | Do not use CHC |
| Current or previous deep-vein thrombosis/pulmonary embolism, including established anticoagulant therapy | 4 | Family history alone in a first-degree relative is MEC 2 |
| Known thrombogenic mutation (e.g. factor V Leiden, prothrombin mutation, protein S, protein C or antithrombin deficiency) | 4 | Do not use CHC |
| Major surgery with prolonged immobilisation | 4 | Without prolonged immobilisation MEC 2 |
| Current or previous ischaemic heart disease; previous stroke | 4 | Do not use CHC |
| Complicated valvular heart disease (pulmonary hypertension, risk of atrial fibrillation or history of endocarditis) | 4 | Uncomplicated valvular disease is MEC 2 |
| Systemic lupus erythematosus with positive or unknown antiphospholipid antibodies | 4 | Do not use CHC |
| Migraine with aura, at any age | 4 | Do not use CHC |
| Migraine without aura, age < 35 | S 2 / C 3 | New headaches or marked changes in headaches must be assessed |
| Migraine without aura, age ≥ 35 | S 3 / C 4 | Do not start; continuation is not recommended |
| Current breast cancer | 4 | Past breast cancer with no evidence of disease for at least 5 years: MEC 3 |
| Diabetes with nephropathy, retinopathy, neuropathy, other vascular disease or duration > 20 years | 3/4 | Depends on disease severity |
| Current or medically treated symptomatic gall-bladder disease | 3 | After cholecystectomy MEC 2 |
| Previous combined-pill-related cholestasis | 3 | Previous pregnancy-related cholestasis alone is MEC 2 |
| Acute viral hepatitis or flare | S 3/4 / C 2 | Starting category depends on severity; it is not a blanket MEC 4 condition |
| Severe decompensated cirrhosis; hepatocellular adenoma; malignant liver tumour | 4 | Do not use CHC |
| Certain anticonvulsants (phenytoin, carbamazepine, barbiturates, primidone, topiramate, oxcarbazepine), lamotrigine, or rifampicin/rifabutin | 3 | Relevant interactions or reduced efficacy; review the medicine and contraceptive method individually |
S = starting, C = continuing. A 3/4 category requires individual classification; it does not mean “somewhere between 3 and 4” without further assessment.
Commonly misunderstood risks
- DVT/PE only in a first-degree relative: MEC 2
- Obesity with BMI ≥ 30 as an isolated factor: MEC 2 — WHO does not automatically classify BMI ≥ 35 as MEC 3
- Major surgery without prolonged immobilisation: MEC 2; minor surgery without immobilisation: MEC 1
- Superficial venous thrombosis: MEC 2; varicose veins: MEC 1
- Breastfeeding from 6 months after birth: MEC 2
- Age ≥ 40 as an isolated factor: MEC 2
Several individually lower risks may result in a less favourable overall assessment. Blood-pressure measurement, personal and family history, and a complete medicines list are therefore part of prescribing.
Warning signs while using CHC — the correct emergency route
- sudden shortness of breath, chest pain, coughing blood or collapse
- sudden one-sided weakness/paralysis, facial droop, difficulty speaking or understanding
- sudden loss of vision or new severe neurological symptoms
- a sudden, unusually severe “worst” headache, especially with neurological symptoms
- sudden severe abdominal pain, especially with circulatory problems or fainting
A newly painful, swollen leg on one side needs medical assessment on the same day. If this occurs with shortness of breath, chest pain or circulatory problems, call 144. Otherwise, call the practice during opening hours on 044 525 20 60; outside opening hours in Canton Zurich, call Aerztefon 0800 33 66 55 (24/7).
Checklist (voluntary)
This summary is based on WHO MEC 6 and the SGGG checklist and is intended to help you prepare for a first prescription or a change of prescription. It does not replace an individual medical assessment.
Please let us know if any of the following applies to you:
- Smoking (especially from age 35)
- Migraine (especially with aura) or new severe headaches
- High blood pressure or blood-pressure medication
- Thrombosis or pulmonary embolism in your own history or in close relatives
- Known clotting disorder
- Planned major surgery or prolonged immobilisation (e.g. a cast, being bedbound)
- Diabetes, markedly raised blood lipids, gall-bladder or liver disease
- Breast cancer, cardiovascular disease, stroke, complicated valvular heart disease or lupus
- Breastfeeding or a recent pregnancy/birth (please give the date)
- Medicines or supplements that can affect how it works (e.g. certain anti-epileptic drugs, St John's wort)
Tip: if you are unsure whether something is relevant, mark it anyway — we will discuss it together.
Before your appointment
Please bring with you, or think through in advance:
- Your current list of medicines (including herbal preparations, St John's wort)
- Family history: thrombosis, pulmonary embolism, breast cancer, stroke, heart attack before age 50
- Your own previous illnesses and earlier operations
- Your current blood pressure (can be measured at a pharmacy)
- Your approximate BMI (weight / height)
- Migraine yes/no, with/without aura
- Smoking status
- Date of your last period / cycle length (if known)
- Any questions or preferences regarding cycle control and alternatives (IUD, implant, ring, patch)
Sources
- WHO — Medical eligibility criteria for contraceptive use, 6th edition (2025)
- WHO MEC 6 — complete summary table
- SGGG — CHC checklist for first or new prescription (German)
- Canton Zurich — emergency services (German)
Back to the contraception overview
Last updated: July 2026 · These notes do not replace individual medical advice.