Which contraceptive methods are the most effective?

The most effective reversible methods are the long-acting reversible contraceptives: the etonogestrel implant and the intrauterine devices, both copper and levonorgestrel. They beat the pill, patch, and ring because they do not depend on the user remembering anything. Permanent sterilization is also in the top tier.

What is the most effective emergency contraception?

The copper intrauterine device is the most effective emergency contraception and can be placed up to 5 days after unprotected sex. Among pills, ulipristal acetate is more effective than levonorgestrel, especially later in the window and at higher body weight. Levonorgestrel is most effective within 72 hours.

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Gynecology · Family Planning

Contraception

Q: Who should not take estrogen-containing contraception?

Estrogen is avoided in migraine with aura, a smoker who is 35 or older, a history of venous thromboembolism or known thrombophilia, uncontrolled hypertension, a history of stroke or heart disease, current breast cancer, and the early postpartum period. These patients use a progestin-only method or an intrauterine device.

A handful of methods, three mechanisms, and one tier of star performers that work no matter how forgetful you are. Learn how each one stops a pregnancy, who can never touch estrogen, and the emergency options when the plan fails.

The Setup

Three Ways to Stop a Pregnancy

Every method works through one or more of three levers: stop the egg from releasing, block the sperm, or make the uterus unwelcoming. Match the lever to the method and the side effects make sense.

A 19-year-old woman wants the most effective birth control but admits she forgets pills constantly and hates the idea of a daily routine. She has no medical problems and may want children in a few years.

Which option best fits a woman who cannot rely on remembering anything?

Lever one: stop ovulation. Estrogen and progestin together (the combined pill, patch, and ring) suppress the pituitary so LH and FSH stay low and no egg is released. They also thicken cervical mucus and thin the lining. Progestin-only methods lean mostly on the mucus and lining, and the higher-dose ones (the implant, the injection) also block ovulation.

Lever two: block the sperm. The copper IUD is hormone-free. Copper ions create a local inflammatory reaction that is toxic to sperm, so fertilization rarely happens. Condoms and diaphragms are physical barriers, and condoms add the bonus of protecting against sexually transmitted infections, which no hormonal method does.

Lever three: make the uterus unwelcoming. Progestins thicken cervical mucus into a plug sperm cannot cross and thin the endometrium. The levonorgestrel IUD does this powerfully right where it sits, which is why it makes periods lighter and can treat heavy bleeding.

Efficacy tiers. The single biggest predictor of failure is whether a method depends on the user. The top tier removes the human from the loop.

The long-acting reversible methods sit on top precisely because they do not depend on a daily decision. That user-independence is the whole reason they outperform the pill.

The Toolbox

The Methods, One by One

Know the headline fact and the headline side effect for each. Tap each card.

Combined pill, patch, ring

Tap to reveal

Estrogen plus progestin suppress ovulation. Bonuses: lighter, more regular periods and lower ovarian and endometrial cancer risk. The catch is the estrogen contraindications and a small rise in clot risk.

Progestin-only pill

Tap to reveal

No estrogen, so it is safe in breastfeeding and in women with estrogen contraindications. The catch is strict timing; it must be taken at the same time each day.

Etonogestrel implant

Tap to reveal

A progestin rod under the arm and the most effective reversible method, lasting about 3 years. The common nuisance is unpredictable spotting.

DMPA injection

Tap to reveal

A progestin shot every 3 months. Often causes amenorrhea and weight gain, with a reversible drop in bone density and a delayed return of fertility after stopping.

Levonorgestrel IUD

Tap to reveal

A progestin IUD that thins the lining, so it makes periods lighter and is used to treat heavy menstrual bleeding. Lasts several years.

Copper IUD

Tap to reveal

Hormone-free, lasts about 10 years, and doubles as the best emergency contraception. The trade-off is heavier periods and cramps. Avoid in Wilson disease or copper allergy.

From the Attending No hormonal method protects against sexually transmitted infections. A patient on the most effective implant or IUD still needs condoms if she has any infection risk. Pregnancy protection and infection protection are two different jobs. Cover both.

Clinical Images

Intrauterine devices, copper and hormonal

Intrauterine device with strings · tap

Combined oral contraceptive pack · tap

The Guardrails

Who Cannot Take Estrogen

Most contraceptive clinical questions hide here: a patient with a reason to avoid estrogen who needs a progestin-only method or an IUD instead. Estrogen raises clot risk, so its danger list is built around clotting and the vessels.

The estrogen no-go list. Avoid estrogen-containing methods in migraine with aura (raises stroke risk), a smoker who is 35 or older, a history of venous thromboembolism or a known clotting disorder, uncontrolled hypertension, a history of stroke or heart disease, current breast cancer, the early postpartum period (the first weeks, when clot risk is highest), and active liver disease. These patients use progestin-only pills, the implant, the injection, or an IUD.

Work the cases. Each one hides a contraindication. Try before you reveal.

A 28-year-old woman with migraines that include visual aura wants to start the pill. Best advice?

Migraine with aura plus estrogen raises stroke risk, so combined methods are out. She can safely use a progestin-only pill, the implant, the injection, or either IUD. Migraine with aura means no estrogen, but plenty of progestin options remain.

A 38-year-old woman who smokes a pack a day asks for the combined pill. Best decision?

A smoker who is 35 or older has a sharply higher clot and cardiovascular risk on estrogen, so combined methods are contraindicated. Progestin-only methods and IUDs are safe. Smoker, 35 or older equals no estrogen.

A woman 2 weeks after delivery who is breastfeeding wants contraception. Best choice?

Clot risk is highest in the first weeks after delivery, so estrogen is avoided early postpartum. A progestin-only pill, the implant, or an IUD is preferred and is compatible with breastfeeding. Early postpartum equals avoid estrogen; reach for progestin or an IUD.

Match the patient to the method. The table collects the classic pairings.

Patient	Avoid	Reach for
Migraine with aura	Estrogen (stroke risk)	Progestin-only pill, implant, IUD
Smoker, 35 or older	Estrogen (clot, cardiac risk)	Progestin-only method or IUD
Prior venous clot or thrombophilia	Estrogen	Progestin-only method or IUD
Heavy menstrual bleeding	Copper IUD (worsens bleeding)	Levonorgestrel IUD or combined pill
Wants nonhormonal	All hormones	Copper IUD
Wilson disease or copper allergy	Copper IUD	Levonorgestrel IUD or progestin method

The Backup Plan

Emergency Contraception

After unprotected sex, the goal is to delay or block ovulation, or to stop implantation. There is a clear order of effectiveness, and one method wins on every axis.

The copper IUD wins. The copper IUD is the most effective emergency contraception and can be placed up to 5 days after unprotected sex. It works whether or not ovulation has already happened, because copper is toxic to sperm and prevents implantation, and it has the bonus of becoming her ongoing contraception. It is the best answer when maximum effectiveness or long-term coverage is the goal.

The pills. Among oral options, ulipristal acetate (a progesterone receptor modulator) is more effective than levonorgestrel, works up to 5 days, and holds up better later in the window and at higher body weight. Levonorgestrel 1.5 mg is available without a prescription, works best within 72 hours, and loses effectiveness with higher body weight. All the pills work mainly by delaying ovulation, so they fail if ovulation has already occurred, which is exactly why the copper IUD is the more reliable choice.

Option	Window	Key point
Copper IUD	Up to 5 days	Most effective; works after ovulation; becomes ongoing contraception
Ulipristal acetate	Up to 5 days	More effective than levonorgestrel, including later and at higher weight
Levonorgestrel 1.5 mg	Best within 72 hours	Over the counter; less effective at higher body weight

From the Attending Emergency contraception is not an abortion. The pills work by delaying ovulation, so they prevent a pregnancy from starting; they do not end an established one. That is why timing matters and why the copper IUD, which also blocks implantation, is the most reliable. Prevent, do not end. Offer the copper IUD when she wants both the best odds and a method going forward.

Board Trap Do not give estrogen to a patient who has a clean estrogen contraindication just because she asks for the pill, and do not put a copper IUD in a woman with heavy painful periods who would do better with the levonorgestrel IUD. The classic trap also pairs DMPA with a teenager worried about bone health: the bone loss is real but reversible, and it is not an absolute contraindication. Read the patient first, then match the method. The contraindication picks the method, not the patient request.

Prove It

Board Walkthrough

Original clinical vignettes, 5 dealt per round, answer choices shuffled, never repeating within a round. Tap a wrong answer first to see why it almost works, then read the glowing clues.

Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO · Last reviewed June 2026

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