Introduction
Contraception lets people choose if and when to have children. Effectiveness is given by the Pearl index (pregnancies per 100 woman-years) or the failure rate with typical use. The most effective methods are the long-acting reversible contraceptives (LARC), which do not depend on daily use.
Combined hormonal contraception: contraindications (UKMEC 4)
- Migraine with aura; smoker aged ≥ 35 (≥ 15 cigarettes a day).
- History of venous thromboembolism, thrombophilia, major surgery with immobilisation.
- Hypertension ≥ 160/100, ischaemic heart disease, stroke, complicated valvular disease.
- Current breast cancer, severe liver disease, less than 3 weeks postpartum (6 weeks if breastfeeding).
Side effects: nausea, breast tenderness, breakthrough bleeding; small increase in VTE (higher with some progestogens), stroke and breast and cervical cancer risk. Enzyme-inducing drugs (rifampicin, some antiepileptics) reduce effectiveness.
Missed pill rule (combined)
One pill missed: take it as soon as possible and continue. Two or more missed: take the last missed pill, use condoms for 7 days, and consider emergency contraception if pills were missed in the first week after the pill-free interval.