Why P2 may fail: Common reasons and what to do next

Introduction

Postinor-2, commonly known as P2, is an emergency contraceptive taken after unprotected sex or contraceptive failure, such as a condom breaking.

While P2 is highly effective when used correctly, it is not foolproof. There are instances where it may fail to prevent pregnancy.

This article breaks down why P2 may not always work, the factors that can influence its effectiveness, and what steps to take if you suspect it has failed.

How P2 works

Mechanism of action

P2 primarily works by preventing or delaying ovulation — the release of an egg from the ovary.

Without an egg available for fertilisation, pregnancy cannot occur. In some cases, P2 may also prevent fertilisation or stop a fertilised egg from implanting in the uterus.

It is important to note that P2 is most effective when taken as soon as possible after unprotected intercourse. The longer you wait, the less likely it is to work effectively.

Timing matters

The effectiveness of P2 decreases significantly over time. Ideally, it should be taken within 24 hours after unprotected sex.

However, it can still be effective up to 72 hours later, though with reduced success rates. After 72 hours, the chances of preventing pregnancy drop considerably, making early action critical.

Common reasons why P2 may fail

Taking it too late

Waiting too long to take P2 increases the risk of pregnancy. If ovulation or fertilisation has already occurred before the pill is taken, P2 may not be able to prevent pregnancy.

Vomiting after taking P2

Vomiting within two hours of taking P2 can interfere with the body's ability to absorb the medication, reducing its effectiveness. If vomiting occurs during this window, it is advisable to take another dose immediately to ensure protection.

Being close to ovulation

P2 is less effective if you are already close to or have just ovulated when you take it. Since its main function is to delay ovulation, it cannot undo an ovulation that has already happened.

Understanding your menstrual cycle can help estimate when you are most fertile and assess the potential effectiveness of P2.

Body weight and BMI

Research suggests that P2 may be less effective in individuals with higher body weight or a high Body Mass Index (BMI).

Although studies are ongoing, some experts recommend discussing alternative emergency contraception methods with a healthcare provider if you fall into this category.

Drug interactions

Certain medications can reduce the effectiveness of P2. These include some anti-seizure drugs, antibiotics like rifampicin, and herbal remedies such as St. John's Wort.

If you are taking any other medications, it is crucial to consult a healthcare provider about possible interactions before relying on P2.

What to do if you think P2 has failed

Signs to watch for

If you experience early signs of pregnancy, such as missed periods, nausea, or breast tenderness after taking P2, it could suggest that the pill did not work.

It is generally recommended to take a pregnancy test about three weeks after the episode of unprotected sex to confirm whether or not you are pregnant.

Seeking medical advice

If you are concerned that P2 may have failed, seeking prompt medical advice is crucial.

A healthcare provider can offer guidance on next steps, including additional emergency contraception methods, ongoing birth control options, and early prenatal care if needed.

How to improve the effectiveness of P2

Taking It early

The earlier you take P2 after unprotected sex, the higher its chances of preventing pregnancy. Ideally, aim to take the pill within the first 24 hours.

Considering alternative options

In some cases, especially if you are near ovulation, alternative emergency contraception like a copper intrauterine device (IUD) may offer better protection. A copper IUD can be inserted up to five days after unprotected sex and is highly effective.

Using regular contraception

While P2 is a helpful backup, it should not replace regular birth control methods. Consistent use of contraception such as pills, implants, or IUDs provides ongoing protection and reduces the need for emergency measures.

Conclusion

While P2 is a valuable tool for preventing pregnancy after unprotected sex or contraceptive failure, it is not 100% effective. Timing, biological factors, and external influences like drug interactions or vomiting can all affect its success.

If you are concerned about P2 failure, seek medical advice promptly. For long-term peace of mind, consider adopting a regular contraceptive method to minimise the risk of future emergencies.