How Does Plan B Work A Clear Guide to the Emergency Contraceptive Pill

What Is Plan B?

Plan B is a levonorgestrel‑based emergency contraceptive (EC) pill that can be taken after unprotected sex to prevent an unintended pregnancy. It is available over‑the‑counter in many countries and is designed for occasional, not regular, use.

Mechanism of Action: How the Pill Stops Pregnancy

The active ingredient, levonorgestrel, is a synthetic hormone that works in three main ways:

• Inhibits ovulation: It stops the ovary from releasing an egg, which is the most common way it prevents fertilisation.
• Blocks fertilisation: If an egg has already been released, levonorgestrel can alter the cervical mucus, making it harder for sperm to reach the egg.
• Prevents implantation: Should fertilisation occur, the hormone can change the uterine lining, reducing the chance that a fertilised egg will implant.

Plan B does not terminate an existing pregnancy; it only works before implantation takes place.

Timing and Effectiveness

For maximum efficacy, Plan B should be taken as soon as possible after unprotected intercourse. The pill is:

• 95% effective when taken within 24 hours.
• About 85% effective if taken between 24–48 hours.
• Still around 58% effective up to 72 hours after the event.

Because the hormone’s ability to prevent ovulation declines over time, the sooner you take the pill, the better the odds of avoiding pregnancy.

Side Effects and Safety

Most users experience mild, short‑lasting side effects such as:

• Nausea or slight stomach cramps.
• Headache or dizziness.
• Temporary changes in menstrual bleeding.

These symptoms typically resolve within a few days. Plan B is safe for most women, including those who are breastfeeding, but it should not replace regular contraceptive methods.

Important Considerations

While Plan B is a reliable backup, keep these points in mind:

• It does not protect against sexually transmitted infections (STIs).
• Repeated use may cause menstrual irregularities; consider a long‑term birth control method for ongoing protection.
• If you vomit within two hours of taking the pill, consult a healthcare professional – a repeat dose may be needed.

In summary, Plan B works by delaying ovulation, hindering fertilisation, and altering the uterine environment to prevent implantation. Taking it promptly maximises its effectiveness, making it a valuable option for emergency contraception when you need it most.

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