Contraception

• Contraception prevents pregnancy. Methods fall into several families: combined hormonal contraception (pill, patch, ring), progestogen-only methods (pill, implant, injection), intrauterine devices (copper or levonorgestrel), barrier methods and spermicide, fertility awareness, lactational amenorrhoea, and permanent sterilisation.
• Effectiveness depends as much on the user as on the method: long-acting reversible contraception (implant, IUD, injection) has first-year pregnancy rates under 1 per 100 women, while daily or per-sex methods have higher typical-use failure because of missed doses or inconsistent use. ^{[2] [10]}
• Combined hormonal contraception suits many healthy women but is unsafe with a history of venous thromboembolism (VTE), certain migraines, liver disease and some cancers; progestogen-only and non-hormonal methods carry fewer vascular risks and suit more women.
• Emergency contraception works after unprotected sex: a copper IUD is the most effective, ulipristal acetate works up to 5 days and levonorgestrel up to 3 days.
• Contraceptive choice after childbirth has its own timetable: a method should be in place by day 21, and combined hormonal contraception is delayed to 6 weeks if breastfeeding or if VTE risk is present. ^[9]

By the end of this topic you should be able to:

1. Explain the mechanism by which each contraceptive family prevents pregnancy.
2. Name the members and usual adult doses of the main hormonal and intrauterine methods.
3. Compare methods by typical and perfect-use efficacy, advantages and adverse effects. ^[10]
4. List the common contraindications and how they are graded by UKMEC/US MEC categories. ^[1]
5. Counsel on drug interactions, renal or hepatic impairment, and use in pregnancy and breastfeeding.
6. Manage emergency contraception and postpartum contraception, including LAM and timing.
7. Recognise the common exam traps and avoid them.

Contraception is the prevention of pregnancy. It may be requested for pregnancy spacing, to delay or limit childbearing, for medical indications (for example, to stop ovulation in endometriosis or to regulate cycles), or after sex that has already occurred (emergency contraception). This page takes the drug-class and method-class view: it compares every family, gives the practical details needed at the bedside, and ends with how to choose among them.

A useful two-axis way to think about methods:

• How they work: suppress ovulation; thicken cervical mucus; alter the endometrium; create a hostile environment for sperm or implantation; block sperm physically; or rely on timing and breastfeeding physiology.
• How much they demand of the user: long-acting reversible contraception (LARC: implant, IUD, injection) needs little daily action and is therefore the most effective in real life; user-dependent methods (pills, patch, ring, barriers, natural methods) fail more often because of missed doses.

No method except condoms protects against sexually transmitted infections (STIs), including HIV. Where STI risk exists, condoms (or internal condoms) are added to whatever contraceptive is chosen. ^[2]

The families covered are:

1. Combined hormonal contraception (CHC): combined oral contraceptive pill (COC), transdermal patch, vaginal ring. ^[4]
2. Progestogen-only contraception: progestogen-only pill (POP), subdermal implant, injectable.
3. Intrauterine contraception: copper IUD, levonorgestrel-releasing intrauterine system (LNG-IUS).
4. Barrier and chemical methods: male and female condoms, diaphragm, cervical cap, vaginal sponge, spermicides and vaginal pH modulator.
5. Fertility awareness-based and natural methods, including lactational amenorrhoea (LAM).
6. Permanent contraception: female sterilisation (tubal occlusion) and vasectomy.

LARC (implant, IUD, injectable) is highlighted because it is the most effective method family in practice and is suitable for most women, including adolescents and those who have never given birth. ^[9]

The oestrogen and progestogen components act on the hypothalamic-pituitary axis to reduce luteinising hormone (LH) and follicle-stimulating hormone (FSH). Without the mid-cycle LH surge, ovulation does not occur. CHCs also make cervical mucus thick and hostile to sperm, thin and stabilise the endometrium (the progestogen opposes the proliferative effect of oestrogen), and slow tubal motility. ^[5]

• Implant and injectables suppress ovulation in most cycles and thicken cervical mucus; the endometrium becomes atrophic. ^[7]
• Desogestrel and drospirenone POPs rely mainly on ovulation suppression, plus mucus and endometrial effects. ^[6]
• Traditional levonorgestrel or norethisterone POPs do not reliably stop ovulation; their effect depends on cervical mucus (which stays changed for less than 24 hours after each pill), the endometrium and tubal motility. This short-lived effect explains the 3-hour missed-pill window. ^[6]

• Copper IUD: copper ions are toxic to sperm and ova and also create a sterile inflammatory response in the endometrium that is hostile to implantation; fertilisation is prevented and the device is effective immediately. ^[9]
• LNG-IUS: levonorgestrel is released locally; it thickens cervical mucus, thins the endometrium and may suppress ovulation in some cycles, but the main effect is local. Effects reverse quickly after removal. ^[9]

Male and female condoms block sperm physically; the female condom can be inserted up to 8 hours before intercourse. Diaphragms and cervical caps cover the cervix and are always used with spermicide. Spermicides kill sperm or block ascent; they are placed in the vagina no more than 1 hour before intercourse and left in place at least 6 to 8 hours afterwards. The vaginal pH modulator works without spermicide. ^[2]

These do not use drugs or devices. Fertility awareness methods identify the fertile window (about 9 or more days in a regular 28-day cycle) and avoid intercourse or use barriers on those days, or track temperature and mucus. LAM works because frequent breastfeeding suppresses GnRH and therefore ovulation, but only while all three conditions hold. ^{[2] [4]}

Tubal occlusion (clips, rings, excision or electrocoagulation) or hysteroscopic/systemic non-surgical methods block the fallopian tubes; vasectomy cuts or seals the vas deferens. Neither is intended to be reversible. Vasectomy needs 12 weeks and a zero sperm count before stopping other contraception. ^[2]

• Route and metabolism. CHCs and POPs are oral; the patch and ring use transdermal and vaginal routes; the implant and injectables bypass first-pass metabolism; intrauterine methods act mainly locally with low systemic levels.
• Half-life. Ethinylestradiol and the progestogens in CHC have short half-lives, so missed doses matter within 24 hours. DMPA is given every 13 weeks (NET-EN every 8 weeks) and keeps levels up between doses. The etonogestrel implant releases hormone over 3 years. ^{[7] [9] [2]}
• Enzyme-inducing drugs lower hormone levels and reduce efficacy for CHC and POPs; the effect is pharmacokinetic, so extra precautions or a method change is required.
• Renal and hepatic handling determine cautions and contraindications (see below).

Contraception is indicated for anyone at risk of pregnancy who wishes to avoid it. Method-specific indications include:

• CHC is also used for dysmenorrhoea, menorrhagia, irregular bleeding, acne or hirsutism, endometriosis-related pain, and as an alternative to HRT for menopausal symptoms up to age 50, provided the woman is medically eligible. ^[4]
• POP (desogestrel/drospirenone) may help dysmenorrhoea. ^[7]
• LNG-IUS is licensed for heavy menstrual bleeding and endometrial protection; copper IUDs are non-hormonal and suit women who prefer to avoid hormones.
• Depot medroxyprogesterone can reduce pain in sickle cell disease and may reduce recurrence of endometriosis pain. ^[7]
• Emergency contraception is indicated after unprotected intercourse or suspected contraceptive failure, up to 5 days depending on method.

• Pill (COC): one active tablet daily for 21 days followed by a 7-day hormone-free interval, or a tailored (extended or continuous) regimen. A reasonable first-line product is one containing 30 micrograms or less of ethinylestradiol with levonorgestrel or norethisterone. ^[4][5]
• Patch: one patch weekly for 3 weeks, no patch in week 4.
• Vaginal ring: one ring for 3 weeks, then removed for 1 week.
• The non-pill CHC methods (patch, ring) are useful when compliance with daily pills is difficult. ^[5]

• POP: one tablet daily without a break. Doses in the UK: desogestrel 75 micrograms; drospirenone 4 mg (24 active tablets then 4 placebo); levonorgestrel 30 micrograms; norethisterone 350 micrograms. ^[6]
• Implant: a single subdermal rod releasing etonogestrel, effective for 3 (and, per current licence and FSRH, often up to 5) years. ^[9] Serum levels rise and ovulation is suppressed within about 24 hours.
• Injectables: depot medroxyprogesterone acetate 150 mg intramuscularly or 104 mg subcutaneously every 13 weeks; norethisterone enantate 200 mg intramuscularly every 8 weeks. ^[7]

• Copper IUD: inserted by a trained clinician; licensed for up to 10 years. ^[2]
• LNG-IUS: levonorgestrel releases locally; licence varies by device, typically 3 to 8 years. ^[2]

• Levonorgestrel: 1.5 mg single oral dose, within 72 hours of unprotected intercourse. ^[8]
• Ulipristal acetate: 30 mg single oral dose, within 120 hours. ^[8]
• Copper IUD: inserted within 5 days for the most effective emergency contraception. ^[8]

• Female sterilisation: tubal occlusion by laparoscopy or at caesarean section.
• Vasectomy: an outpatient procedure under local anaesthetic; azoospermia should be confirmed before abandoning other methods. ^[2]

Hormonal methods share common adverse effects; long-acting methods have method-specific issues.

Adverse effect counselling for CHC must include the small cancer associations: current use slightly increases breast cancer risk, which falls after stopping; use for more than 5 years slightly increases cervical cancer risk; and venous/arterial events remain very uncommon in healthy users. ^[4]

The main clinically important interactions are pharmacokinetic:

• Enzyme-inducing drugs (certain anticonvulsants such as carbamazepine, phenytoin and topiramate at high dose; rifampicin and rifabutin; griseofulvin; St John's wort; some antiretrovirals) reduce levels of CHCs and POPs and can cause method failure. ^[4][6]
• What to do: avoid CHC/POP with enzyme inducers where possible; use a method that is not affected (copper IUD, LNG-IUS, depot injectable, implant, or condoms), or use additional precautions. If oral EC is needed while taking an enzyme inducer, a double dose of levonorgestrel (3 mg) is recommended when copper IUD and ulipristal are unsuitable. ^[8]
• Drugs that need monitoring with drospirenone POP: ACE inhibitors, angiotensin receptor blockers, potassium-sparing diuretics, NSAIDs and potassium supplements, because of the hyperkalaemia risk. ^[6]
• Malabsorption: severe vomiting or diarrhoea within a few hours of taking a pill may impair absorption; follow missed-pill rules or use a non-oral method. ^[6]
• Myth to correct: antibiotics that are not enzyme inducers (including broad-spectrum penicillins and tetracyclines) do not reduce CHC or POP efficacy. ^[5]
• Lamotrigine, olanzapine, theophylline and similar drugs may have level changes with CHC; check the BNF/FNR interaction checker. ^[5]

Eligibility is graded in four categories, following the UK and US Medical Eligibility Criteria, which are adapted from WHO MEC 6th edition (2025): ^[1][3]

• Category 1: no restriction.
• Category 2: advantages generally outweigh risks.
• Category 3: risks usually outweigh advantages (use only if no better method is available or acceptable, with careful follow up).
• Category 4 (unacceptable health risk, do not use): conditions listed below.

Key contraindications, especially for combined hormonal contraception:

• Vascular: history of VTE, thrombophilia, arterial vascular disease, stroke or myocardial infarction, migraine with aura, age 35 years or older and smoking 15 or more cigarettes per day, systolic BP 160 or diastolic 100 or higher, complicated valvular heart disease, peripartum cardiomyopathy. ^[1]
• Liver: decompensated cirrhosis, hepatocellular adenoma, hepatocellular carcinoma. ^[1]
• Breast cancer: current or within 5 years. ^[1]
• Pregnancy, or less than 3 weeks postpartum in general (6 weeks if breastfeeding). ^[9]
• Major surgery with prolonged immobilisation and long-haul travel with additional VTE risk factors. ^[4]

A full MEC condition table is in the CDC US MEC 2024 and UKMEC 2025 documents; consult the latest version rather than memorising the whole matrix. ^[1]

In general, progestogen-only methods and intrauterine methods are usable by most women with vascular or metabolic disease (often category 1 or 2), which is why they are alternatives when CHC is unsafe. ^[1][3]

• Hormonal contraception is not indicated in pregnancy; stop the method if pregnancy is diagnosed. Missed pills and irregular bleeding should prompt a pregnancy test when indicated.
• Contraceptives do not terminate an established pregnancy.
• A pregnancy that occurs with an IUD in place should be managed by removing the device if the threads are visible, and by excluding ectopic pregnancy if pain or bleeding occurs.

• Progestogen-only methods can be used at any time after birth, including immediately, with no adverse effect on lactation, infant growth or development. ^[9]
• Combined hormonal contraception should be avoided for the first 3 weeks after birth and delayed to 6 weeks if breastfeeding; use earlier (from 21 days) is reasonable in non-breastfeeding women without VTE risk. ^[9]
• Copper and levonorgestrel IUDs can be inserted immediately after delivery. ^[9]

• Drospirenone POP is contraindicated in severe renal impairment or acute renal failure and needs caution and potassium monitoring in mild to moderate renal impairment, and in older women or those taking potassium-increasing drugs. ^[6]
• DMPA, the implant, the copper IUD and the LNG-IUS are not significantly affected by renal function. ^[1] Other hormonal methods are metabolised hepatically and do not require renal dose adjustment; nevertheless, individual CKD (nephrotic syndrome, dialysis) changes MEC categories, as the 2024 US MEC detailed. ^[1]
• Emergency contraception doses do not change with renal impairment.

• CHC is contraindicated in significant liver disease: decompensated cirrhosis and hepatocellular adenoma or carcinoma are MEC 4. ^[1]
• Progestogen-only methods are generally avoided in severe hepatic impairment and in liver tumours, though unscheduled bleeding and drug accumulation need assessment; the copper IUD is generally suitable. ^[1][3]
• When liver enzymes are induced by drugs, the pharmacokinetic problem is with CHC and POPs as above rather than liver function itself.

Emergency contraception prevents pregnancy after unprotected sex or contraceptive failure. It works best the sooner it is used; a copper IUD is the most effective. ^[8]

• Copper IUD: insert within 5 days (or within 5 days of the earliest estimated ovulation, if later). It can then be kept for ongoing contraception.
• Ulipristal acetate 30 mg: one dose, up to 120 hours (5 days) after intercourse; more effective than levonorgestrel, especially later in the 5-day window and in women with higher BMI; pregnancy rate after use is about 1-2%. ^[8]
• Levonorgestrel 1.5 mg: one dose, up to 72 hours (3 days) after intercourse; pregnancy rate after use is about 0.6-2.6%. ^[8]

Practice points:

• Offer the copper IUD first where feasible; if declined or not possible, offer ulipristal, then levonorgestrel. ^[8]
• BMI and body weight. Copper IUD is unaffected. If using levonorgestrel and BMI is above 26 kg/m2 or weight above 70 kg, offer ulipristal (or a double dose of levonorgestrel, 3 mg) if copper IUD and ulipristal are unsuitable. Double-dose ulipristal is not recommended. ^[8]
• Breastfeeding. Progestogen-only EC (levonorgestrel or ulipristal) can be used from day 21 postpartum. Current UK guidance advises that no interruption of breastfeeding is needed after a single dose of ulipristal for EC; earlier guidance advised expressing and discarding milk for 7 days. Other authorities (for example, CDC) advise interrupting for 24 hours. Counsel according to the guideline your service follows and the setting. ^{[9][11] [2]}
• Enzyme-inducing drugs. Oral EC may be less effective; use copper IUD if possible, otherwise a double dose of levonorgestrel. ^[8]
• Starting ongoing contraception. Quick-start an effective method immediately, because EC only covers the current act. The choice and timing depend on which EC was used: after ulipristal, start the next hormonal method after 5 days (copper IUD can be inserted immediately). ^[8]
• Take a pregnancy test 3 weeks later, or sooner if the next period is late, lighter than usual, or associated with abdominal pain.

Childbirth does not confer prolonged infertility: ovulation can occur before the first bleed, even in non-breastfeeding women, and an interpregnancy interval of under 12 months is associated with prematurity and small-for-gestational-age babies. ^[9]

• A contraceptive method should be in place by day 21 after birth (before day 21 pregnancy is not expected to result in a viable pregnancy). ^[9]
• Progestogen-only methods (pill, implant, injection, LNG-IUS) can start at any time, including immediately postpartum, and have no adverse effect on lactation. ^[9]
• Combined hormonal contraception can start at 21 days if not breastfeeding and without extra VTE risk; at 6 weeks if breastfeeding. Avoid combined methods for 6 weeks if VTE risk factors exist (immobility, BMI 30 or above, caesarean delivery, pre-eclampsia, transfusion, PPH, smoking). ^[9]
• Copper or LNG IUD can be inserted within 10 minutes of placental delivery, or within 48 hours after birth; otherwise delay to 28 days because insertion between 48 hours and 28 days carries higher risks. Immediate insertion has higher expulsion rates, so follow-up is needed. ^[9]
• Lactational amenorrhoea method (LAM) is highly effective while a woman is under 6 months postpartum, amenorrhoeic, and fully breastfeeding (exclusive or almost exclusive, day and night). It ends when any criterion fails: menstruation returns, supplementary feeding starts or increases, night feeds stop, a dummy or pacifier is introduced, or 6 months elapse. ^[2][9]
• Diaphragm should not be fitted until at least 6 weeks postpartum. Condoms are safe at any time. Sterilisation should be consented well in advance, and women should be told about LARC alternatives and the higher regret rate with early postpartum sterilisation. ^[9]

• Adolescents. LARC is safe and highly effective in adolescents, including those who have never given birth; it reduces pregnancy more than user-dependent methods. Consent and confidentiality rules are local. ^[9]
• Older women. CHC may be used by medically eligible women up to age 50 as an alternative to HRT; after 50 safer alternatives exist. ^[4] Fertility is negligible from age 55 (spontaneous conception at that age is exceptionally rare). ^[12]
• Sickle cell disease. DMPA and LARC are preferred; DMPA may reduce sickle cell pain. ^[7]
• Women living with HIV. Hormonal methods and IUDs are generally usable; choices with antiretroviral or PrEP regimens and integrase inhibitors affect LNG-IUS eligibility, and dual protection (condoms) is essential. ^[3]
• Organ transplantation, chronic kidney disease, hypertension, migraine with aura. Follow the current UKMEC/US MEC tables. ^[1][3]

In any setting where health-worker capacity is limited, train staff to insert implants and IUDs, keep a supply of condoms, and ensure women know when to return for bleeding problems, suspected pregnancy or warning symptoms.

• Contraception prevents pregnancy; nothing except condoms also prevents STI and HIV.
• LARC (implant, IUD, injection) has the lowest real-world pregnancy rates because it needs little daily action.
• Combined hormonal contraception works by suppressing ovulation via LH/FSH; it is highly effective with perfect use but less so with typical use.
• Progestogen-only methods rely on ovulation suppression (implant, injectable, desogestrel/drospirenone POP) or cervical mucus (traditional POPs), which is why missed-pill windows differ. ^[6]
• Copper IUD is instantly effective, hormone-free, contraceptive for up to 10 years, and the most effective emergency method.
• LNG-IUS thins the endometrium, often reduces bleeding, and is effective for 3-8 years. ^[2]
• CHC is contraindicated in VTE, migraine with aura, liver tumours, decompensated cirrhosis, current breast cancer, pregnancy and the first 3 weeks postpartum (6 weeks if breastfeeding). ^[1]
• Progestogen-only methods have few vascular contraindications and suit most women with medical disease.
• Enzyme inducers reduce CHC and POP efficacy; non-enzyme-inducing antibiotics do not.
• Emergency contraception: copper IUD (most effective, 5 days), ulipristal 30 mg (5 days), levonorgestrel 1.5 mg (3 days); adjust for high BMI/weight with levonorgestrel.
• By day 21 after birth, a contraceptive method should be in place; combined methods are delayed to 6 weeks if breastfeeding or if VTE risk is present.
• LAM is highly effective only under 6 months postpartum, amenorrhoeic and fully breastfeeding. ^[2]
• Worldwide, offer the best single-visit effective method, protect against STI/HIV with condoms, and use UKMEC/US MEC category tools for eligibility.

Contraception is linked to antepartum fetal surveillance, antenatal care and preconception care, postnatal care and contraception after birth, sexual health and STI management, pregnancy, bleeding problems, migraine and vascular disease, liver disease and renal disease (discussed as MEC categories in this page).