Obstetrics and Gynaecology chapters
Contraception: reversible and irreversible, male and female
Every method of contraception by mechanism, how well each works in typical use, who must not use the combined pill, missed pill rules, emergency contraception, sterilisation and vasectomy.
- The most effective methods are long-acting reversible contraception: implant, intrauterine device and injectable, where typical use is almost as good as perfect use.
- Combined methods stop ovulation by negative feedback on FSH and LH; progestogen methods vary, but all thicken cervical mucus, and the LNG-IUD mainly atrophies the endometrium.
- The best emergency method is a copper device, usable up to 5 days after ovulation; the oral options are ulipristal within 120 hours and levonorgestrel within 72 hours, both of which work by delaying ovulation.
On this page
Overview
No method is completely effective. Efficacy follows the mechanism; effectiveness depends on correct, consistent use. Many women who present pregnant were using something: a weak method such as a condom, or a good method used badly. Without contraception about 85 of 100 couples conceive within a year.
How the methods work
| Target | Methods |
|---|---|
| Prevent ovulation | Combined methods, injectable, implant, oral emergency contraception, lactational amenorrhoea |
| Stop sperm meeting the oocyte | Female sterilisation, vasectomy |
| Prevent implantation | Copper device and LNG-IUD |
| Block or kill sperm | Condoms, diaphragm and cap, spermicides, and the mucus effect of progestogens |
| Avoid the fertile days | Fertility awareness methods |
Failure rates
| Method | Typical use (%) | Perfect use (%) |
|---|---|---|
| None | 85 | 85 |
| Fertility awareness methods | 15 | - |
| Male condom | 13 | 2 |
| Female diaphragm | 17 | 16 |
| Combined pill, patch or ring, or progestogen-only pill | 7 | 0.3 |
| Progestogen-only injectable | 4 | 0.2 |
| Copper intrauterine device | 0.8 | 0.6 |
| Female sterilisation | 0.5 | 0.5 |
| 52 mg LNG-IUD | 0.1 (same in perfect use) | 0.1 |
| Progestogen-only implant | 0.1 (same in perfect use) | 0.1 |
For long-acting reversible contraception typical use failure is almost the same as perfect use, because nothing depends on the user once it is fitted; for short-acting methods the two diverge widely, so quote typical figures to a woman.
Discontinuation, not failure, is the main problem with short-acting methods: about half of users stop the pill, patch, ring or injectable within a year, while 80% or more still use an implant or device at a year.
Safety and eligibility
The WHO medical eligibility criteria grade each condition against each method in four categories: 1 no restriction, 2 advantages generally outweigh the risks, 3 risks usually outweigh the advantages, 4 an unacceptable health risk, that is absolutely contraindicated.
Examples of category 4 for combined hormonal contraception: smoking over the age of 35; blood pressure over 160/100 mmHg; hypertension with vascular disease; past or present deep vein thrombosis, myocardial infarction or stroke; several serious cardiovascular risk factors; known thrombogenic mutations; current breast cancer. Migraine with aura also rules the pill out, since the aura reflects cerebral vasospasm and stroke risk is higher.
Drug interactions
Enzyme-inducing drugs raise hepatic metabolism and reduce the efficacy of the combined pill, patch and ring, the implant and the progestogen-only pill:
anticonvulsants (carbamazepine, oxcarbazepine, eslicarbazepine, phenytoin, phenobarbital, primidone, topiramate), rifampicin and rifabutin, griseofulvin, and antiretrovirals including protease inhibitors, efavirenz and nevirapine.
Women on these drugs should add condoms, or switch to a method that is not affected: the injectable, the copper device or the LNG-IUD. Most broad-spectrum antibiotics do not reduce the efficacy of the combined pill.
"Rifampicin ruins the pill; the coil does not care."
Combined hormonal contraception
All three forms (pill, patch, ring) inhibit ovulation through negative feedback of oestrogen and progestogen on the pituitary, suppressing FSH and LH, and are similar in effectiveness, safety and side effects.
- Most pills are low dose, with ethinyl oestradiol 15-35 micrograms, as 21 pills then a 7-day break with no hormone (or seven placebo tablets); monophasic is standard. The pill may also be taken continuously, tricycled (three packets back to back) or tailored, which suits a woman with dysmenorrhoea or headaches in the break.
- Progestogen generations: second (levonorgestrel, norethisterone), third (gestodene, desogestrel), fourth (drospirenone, dienogest). Later ones are less androgenic but carry more venous thrombosis risk, so second-generation pills are first choice.
- The patch is changed weekly for 3 weeks then a week off. The ring is the lowest-dose combined method.
Risks and benefits
| Area | Effect |
|---|---|
| Venous thromboembolism | Roughly 5 per 10,000 non-pregnant non-users, 10 per 10,000 pill users, 29-400 per 10,000 in pregnancy and the puerperium; risk is highest in the first year. Ask about personal and family history rather than screening for thrombophilia |
| Arterial disease | Rarer but more serious; rises with age and strongly with smoking |
| Ovarian cancer | Risk roughly halved after 10 years of use, with protection lasting over 15 years after stopping |
| Endometrial and colorectal cancer | Endometrial risk almost halved in ever-users; colorectal risk also lower; death from any cancer 12% lower |
| Breast cancer | Raised during use, falling after stopping, back to never-user level by 10 years |
| Cervical cancer | Reported increase, possibly confounded; screening and vaccination are the answer |
The combined pill reduces ovarian and endometrial cancer risk but raises breast cancer risk while it is being taken. Do not blur the two.
Side effects and missed pills
Women report unexpected bleeding, weight gain, headache, mood change and lower libido, but there is no good evidence that hormonal methods cause weight gain (apart from the injectable in adolescents) or affect mood or libido. Early bleeding is common (about 15%) and settles; beyond 3 months look for polyps, chlamydia or a cavity lesion.
Missed pill rules (monophasic pills containing ethinyl oestradiol):
| Situation | Action |
|---|---|
| One pill missed (24-48 hours late) | Take it as soon as remembered, carry on as usual. Emergency contraception is not usually needed, but consider it where pills were also missed earlier in the pack, or during the final week of the pack before |
| Two or more missed (over 48 hours late) | Take the most recent missed pill at once, carry on as usual, and use condoms, or avoid sex, until seven active pills in a row have been swallowed |
| Missed in week 1 | Consider emergency contraception if there was unprotected sex during the 7-day break or in that first week |
| Missed in week 2 | No emergency contraception needed if the previous 7 days were taken correctly |
| Missed in week 3 | Skip the 7-day break: finish the pack (discard placebos) and start the next pack the next day |
Extra precautions are also needed if a patch is off for 48 hours or a ring is out for more than 48 hours.
Progestogen-only methods
Mechanism depends on dose and route. The injectable, the implant and the desogestrel or drospirenone pills inhibit ovulation; other progestogen-only pills do so inconsistently. All of them thicken the cervical mucus. The LNG-IUD barely affects ovulation; it causes marked endometrial atrophy.
| Method | Detail |
|---|---|
| Progestogen-only pill | Taken every day. Desogestrel and drospirenone pills stop ovulation in 99% of cycles; others in under half and rely on mucus. Side effects: irregular bleeding, simple ovarian cysts, acne. If missed: carry on and use extra precautions for 48 hours, with emergency contraception after unprotected sex in that window |
| Implant (etonogestrel) | Single rod lasting 3 years, placed subdermally in the non-dominant upper arm under local anaesthetic by a trained clinician; it contains barium so it shows on X-ray. No routine follow-up, and fertility returns at once after removal |
| Injectable (depot medroxyprogesterone acetate) | 150 mg intramuscularly or 104 mg subcutaneously, both every 13 weeks, with over 50% amenorrhoea at a year; the subcutaneous form can be self-given. Return of fertility may be delayed up to a year, and there is an early 5% loss of lumbar spine bone density that plateaus and seems reversible |
| LNG-IUD | 52 mg (6 years, and if fitted at 45 or over it may stay to menopause or age 55), 19.5 mg (5 years), 13.5 mg (3 years). Bleeding is unpredictable early, then lighter or absent; the 52 mg device cuts heavy menstrual bleeding by 90% at 12 months and also helps dysmenorrhoea, endometriosis and adenomyosis |
Intrauterine contraception
- Copper device lasts 3 to 10 years by type; fitted at 40 or over it may stay until the menopause.
- Mechanism: a sterile inflammatory reaction, with changes in macrophages, leucocytes, prostaglandins and enzymes in uterine and tubal fluid that are toxic to sperm and egg and hinder sperm transport; implantation is also inhibited.
- Bleeding: the LNG-IUD gives lighter, less painful periods, while the copper device often makes them heavier and more painful; an NSAID or tranexamic acid at menses helps, or switch device.
- Risks of insertion:
| Risk | Figure and notes |
|---|---|
| Perforation | About 1 in 1,000, commoner with an inexperienced fitter, while breastfeeding and within 6 months of delivery: missing threads with severe pain after insertion, no device on ultrasound, located on abdominal X-ray, then laparoscopic retrieval |
| Expulsion | 1 in 20 in the first 3 months, less later; teach self-checking for threads |
| Infection | About 1 in 100 in the first 3 weeks, then no higher than a non-user; usually leave the device, give antibiotics and test for infection |
| Missing threads | Pregnancy, expulsion or perforation: test, cover, then speculum or ultrasound |
- Ectopic pregnancy: the overall risk is much lower than with no contraception, but if pregnancy does occur with a device in place the relative chance of it being ectopic is high, so scan. Remove the device where possible, because miscarriage, preterm delivery, septic abortion and chorioamnionitis follow if it stays. Devices do not delay return of fertility or cause infertility.
Barrier methods and spermicides
- Male condoms are the only reversible male method and the only method that protects against sexually transmitted infection including HIV; typical failure is around 24%. The female condom also protects against infection.
- Diaphragm and cap go in before sex, usually with spermicide; typical failure is about 18%, with more discharge and urinary infection in some users.
- Spermicide alone is not recommended: it is weak, and frequent nonoxynol-9 use may raise HIV transmission.
Fertility awareness methods
Needs motivation and regular cycles, so it does not suit women at either extreme of reproductive age, nor those whose periods are irregular; typical failure rates are high.
- Calendar (rhythm) method: from at least six recorded cycles, the first fertile day is the shortest cycle minus 20 and the last is the longest cycle minus 10; a 28-day cycle means abstaining about days 8-18.
- Temperature: basal temperature rises about 0.5 degrees C after ovulation, but infection, exercise and drugs interfere.
- Mucus and other signs: fertile mucus is clear, watery and slippery, turning thick and opaque after ovulation; the cervix softens and rises slightly, and monitors read urinary oestrogen metabolite and LH.
Shortest cycle 26 days, longest cycle 32 days.
First fertile day = 26 − 20 = day 6
Last fertile day = 32 − 10 = day 22
So she must avoid sex from day 6 to day 22, that is 17 days each cycle.
Lactational amenorrhoea and postpartum contraception
- Within 6 months of delivery, amenorrhoeic and fully or nearly fully breastfeeding, the risk of pregnancy is about 2%; after 6 months, or once periods return or feeding reduces, another method is needed. Up to 10% of breastfeeding women conceive, so it is not reliable alone. The mechanism is thought to be inhibition of pulsatile LH release.
- Non-breastfeeding women may ovulate from about day 21, so cover should start then; half have resumed sex by 6 weeks.
- Combined pill: avoid it early, because of puerperal thrombosis risk and effects on milk; the progestogen-only pill is preferred, from about day 21. The injectable may be given in the first 48 hours but causes breakthrough bleeding, so 5-6 weeks is better, and an intrauterine device waits 4-8 weeks for involution, with care since perforation is commoner while breastfeeding.
- Raise contraception at every opportunity, including after a request for abortion (most women ovulate the next month) and after methotrexate for ectopic pregnancy, since that drug is teratogenic. Intervals under 12 months carry more preterm birth, low birth weight and child death.
Emergency contraception
| Method | Window | Notes |
|---|---|---|
| Copper intrauterine device | Up to 5 days after ovulation | The most effective, failure about 1 in 1,000; its endometrial effect prevents implantation. Can be removed once pregnancy is excluded or kept for ongoing contraception |
| Ulipristal acetate 30 mg | Up to 120 hours | Progesterone receptor modulator; more effective than levonorgestrel |
| Levonorgestrel 1.5 mg | Up to 72 hours | Licensed limit is 72 hours |
Both oral methods act by delaying ovulation: sperm already in the tract lose the power to fertilise before an egg is released. It prevents only about two-thirds of the pregnancies that would otherwise occur, so a regular method should be started at once afterwards. Current UK guidance does not endorse the LNG-IUD for this purpose.
Ask how many days have passed. Past 72 hours, levonorgestrel is out; past 120 hours, only a copper device will do.
Irreversible methods
Female sterilisation
Permanent tubal occlusion, usually at laparoscopy with Filshie clips, or at laparotomy such as caesarean section. Counselling points:
- Regard it as irreversible; failure is 1 in 200, similar to long-acting reversible methods, and there is a 1 in 1,000 risk of injury to bowel, bladder or vessels.
- Vasectomy is safer and quicker, with less morbidity, usually under local anaesthetic.
- Some women regret it: risk factors are age under 30, nulliparity, recent pregnancy and relationship problems. It gives no protection against infection.
- Continue contraception until the period after the procedure, since an egg fertilised that cycle could still implant; later pregnancy is rare but the relative chance of it being ectopic is raised.
- Valid consent, taken well in advance when planned with a caesarean section, is essential. After delivery it is better delayed past 6 weeks, when laparoscopic clip sterilisation is less traumatic with a lower failure rate.
Vasectomy
- The vas deferens is interrupted; the no-scalpel method uses a scrotal puncture under local anaesthetic, then division and occlusion with cautery. There is a small risk of scrotal haematoma and infection.
- Semen analysis at 12 weeks confirms absence of sperm, and another method is used until azoospermia is confirmed.
- Failure is about 1 in 2,000, better than female sterilisation. Ejaculate volume barely changes, since sperm add very little volume.
"Her 1 in 200, his 1 in 2,000": vasectomy is the more reliable and the safer operation.
Expect: mechanism of each method and why long-acting ones perform best in typical use; WHO category 4 conditions for combined methods, especially smoking over 35 and migraine with aura; enzyme inducers weakening the pill, patch, ring, implant and progestogen-only pill while the injectable and both devices are unaffected; missed pill rules and skipping the break in week 3; cancer effects in both directions; the injectable delaying fertility and lowering bone density; copper device mechanism with expulsion and perforation figures; emergency contraception windows of 72 and 120 hours with the copper device best; lactational amenorrhoea conditions; and 1 in 200 for tubal occlusion against 1 in 2,000 for vasectomy with semen testing at 12 weeks.
Quick revision
- Long-acting methods are the most effective; typical use nearly matches perfect use.
- Combined methods stop ovulation by pituitary feedback; progestogen methods thicken mucus; the LNG-IUD atrophies the endometrium.
- Category 4: smoking over 35, pressure over 160/100, past thrombosis or stroke, migraine with aura, current breast cancer.
- Enzyme inducers weaken the pill, patch, ring, implant and progestogen-only pill; injectable and devices are unaffected.
- Two or more pills missed: condoms until seven active pills; week 3 means skipping the break.
- Pill lowers ovarian, endometrial and colorectal cancer risk; breast cancer risk rises only during use.
- Injectable may delay fertility a year and lowers bone density about 5% early.
- Copper device: expulsion 1 in 20, perforation 1 in 1,000, early infection 1 in 100.
- Emergency: copper device best, to 5 days after ovulation; ulipristal 120 hours; levonorgestrel 72 hours.
- Tubal occlusion fails 1 in 200; vasectomy about 1 in 2,000, semen analysis at 12 weeks.
Written by The House Job from standard references (Gynaecology by Ten Teachers; Obstetrics by Ten Teachers; Basic and Clinical Pharmacology by Katzung).
FAQ
Why is a copper device the best emergency method?
It acts after ovulation by preventing implantation, fails only about 1 in 1,000, and can stay as ongoing contraception.
A woman on rifampicin wants reliable contraception: what fits?
The progestogen-only injectable, a copper device or an LNG-IUD, since enzyme induction does not reduce their efficacy.
Why must contraception continue after a vasectomy or tubal occlusion?
Sperm persist in the ducts until clearance, shown by semen analysis at 12 weeks; after tubal occlusion an egg fertilised that cycle could still implant.