Classification of Contraceptive Methods

Contraceptive methods can be classified by hormonal content, duration of action, reversibility, mechanism, user dependence and effectiveness tier. A sound classification helps the clinician compare options quickly, explain trade-offs and choose methods that match the patient's medical profile and reproductive plans.

By hormonal content.

• Combined hormonal: combined oral pills, transdermal patch, vaginal ring, combined injectables.

• Progestogen only: progestin-only pills, DMPA intramuscular and subcutaneous, norethisterone enanthate, etonogestrel and levonorgestrel implants, levonorgestrel IUDs.

• Nonhormonal: copper IUD, barrier methods, spermicides, fertility awareness based methods, lactational amenorrhoea method, withdrawal, sterilisation.

By duration.

• Long-acting reversible: implants (3 to 5 years) and IUDs (3 to 12 years depending on device).

• Short-acting: daily pills, weekly patch, monthly ring and combined injectables, two-monthly norethisterone enanthate, three-monthly DMPA.

• Permanent: female sterilisation and vasectomy.

By user dependence. Methods that need no action after provision (implants, IUDs, sterilisation) have almost identical typical and perfect use failure rates. Methods that depend on daily, weekly, coital or calendar action have a wide gap between the two.

Effectiveness tiers with pregnancies in the first year of typical use.

By mechanism. Ovulation suppression, cervical mucus thickening, spermicidal and anti-fertilisation action, barrier, behavioural avoidance of the fertile window, and surgical occlusion.

By timing of use. Methods used before intercourse (all regular methods), at intercourse (condoms, diaphragm, spermicides, withdrawal) and after intercourse (emergency methods).

By who controls use. Methods that a woman can use without partner involvement (implants, IUDs, injectables, pills) are important where partner negotiation is unsafe; DMPA-SC adds the option of self-injection.

Using classification to counsel.

• Present methods from most to least effective while respecting the patient's priorities.

• Highlight what each group does to menstrual bleeding: amenorrhoea is common with DMPA and the levonorgestrel 52 mg IUD; irregular bleeding with implants and progestin-only pills; heavier periods with the copper IUD; regular withdrawal bleeds with combined methods.

• State the return to fertility: immediate for all reversible methods except DMPA, where median delay is 9 to 10 months after the last injection.

• Identify which methods protect against STIs: only external and internal condoms.

Matching group to medical profile. Where oestrogen is contraindicated (postpartum under 21 days, VTE, migraine with aura, hypertension of 160/100 mmHg or more, smoking over 35 at 15 or more cigarettes daily), progestogen-only and nonhormonal methods remain available. Where enzyme inducers are taken long term, DMPA, the IUDs and condoms keep their effectiveness.

Common errors.

• Treating all progestogen-only methods alike: start rules, missed-use windows and bleeding profiles differ by product.

• Grouping DMPA and norethisterone enanthate as interchangeable injections; they have different intervals and are not used alternately.

• Assuming a long-acting method is inappropriate in adolescents or nulliparous women; both groups are eligible for implants and IUDs.

• Presenting withdrawal or fertility awareness methods without stating their failure rates.

Emergency contraception is not a regular method. Repeated use is safe but less effective than any regular method, and frequent users should be offered an ongoing method.

Referral and escalation. Refer patients who want a method not offered at the facility, and those needing permanent methods, to a centre providing them, without delaying an interim method.