Clinical overview
Contraception is among the highest-impact interventions in women's health: it prevents unintended pregnancy and unsafe abortion, allows pregnancy spacing, and reduces maternal mortality. In South Africa, where the HIV and sexually transmitted infection burden is high and unintended pregnancy is common, contraceptive counselling carries an extra dimension — dual protection — and the public sector provides the full range of methods free of charge. This is an HOTS objective because the task is rarely "which method is best" in the abstract; it is matching the right method to the individual woman, integrating her reproductive intentions, her medical eligibility, her STI/HIV risk, her tolerance of bleeding changes, and her own preferences, through genuine shared decision-making.
Two frameworks anchor safe prescribing. Effectiveness is best understood in tiers, and counselling should be honest about the gap between perfect and typical use — the latter is what actually determines pregnancy rates, and it is why the long-acting reversible contraceptives (LARC) — the implant and intrauterine methods — are so dominant: they are "fit-and-forget" and remove the adherence burden. Eligibility is governed by the WHO Medical Eligibility Criteria (MEC), now in its 6th edition (2025), which classifies each method against each condition as Category 1 (no restriction), 2 (advantages generally outweigh risks), 3 (risks generally outweigh advantages — use only if better options unavailable), or 4 (unacceptable health risk — do not use). South Africa's National Contraception Clinical Guidelines (2019) localise this, and the UK FSRH UKMEC is a useful cross-reference. This chapter compares the modalities by mechanism, effectiveness, benefits, risks, and eligibility, then sets out how to choose. It links to Postpartum contraception, HIV counselling, Osteoporosis (DMPA and bone), Heavy menstrual bleeding management (the LNG-IUS), and Termination of pregnancy.
Core knowledge
Effectiveness tiers (typical-use failure in the first year)
| Tier | Methods | Typical-use failure |
|---|---|---|
| Most effective | Implant, LNG-IUS, copper IUD, female & male sterilisation | <1 per 100 |
| Moderately effective | DMPA/NET-EN injectable, COC pill, progestogen-only pill, patch, vaginal ring | ~6–9 per 100 |
| Less effective | Male/female condoms, diaphragm, fertility awareness, withdrawal, spermicide | ~13–21 per 100 |
The implant and IUDs sit in the top tier because their effectiveness does not depend on the user remembering anything — typical and perfect use are nearly identical. For the injectable, pill, patch and ring, the difference between perfect and typical use is large and adherence-driven.
Figure B4.1 — Contraception map comparing typical-use effectiveness, duration, mechanisms, and key counselling trade-offs.
Combined hormonal contraception (CHC) — pill, patch, vaginal ring
- Composition/mechanism: ethinylestradiol (or newer oestrogens) plus a progestogen. Primary action is suppression of ovulation (inhibits the FSH/LH surge); they also thicken cervical mucus and thin the endometrium.
- Non-contraceptive benefits: predictable, lighter, less painful periods; improvement in acne and hirsutism (useful in Hyperandrogenism); reduced functional ovarian cysts; and a durable reduction in ovarian and endometrial cancer risk.
- Risks: a 3–5-fold relative increase in venous thromboembolism (highest in the first year; drospirenone- and third-generation–progestogen pills carry slightly higher VTE risk than levonorgestrel pills), and increased arterial risk (MI, ischaemic stroke) especially in smokers over 35 and in uncontrolled hypertension.
- MEC Category 4 (do not use) examples: migraine with aura, smoking ≥15/day at age ≥35, BP ≥160/100, current/past VTE, known thrombogenic mutation, <6 weeks postpartum and breastfeeding, current breast cancer, complicated valvular heart disease, and active liver disease.