The morning-after pill and menstruation: effects on the menstrual cycle

Written by Marion Goilav

Relecture professionnelle

How does the morning-after pill work? How do I take it? Who can take the pill? What is it used for? Does it delay menstruation? Does it cause side effects in women? We answer all your questions in this article.

What is the morning-after pill?

The morning-after pill is an emergency contraceptive in tablet form. Emergency contraception helps prevent an unwanted pregnancy. It is used in the event of contraceptive failure (e.g. condom breakage, forgotten contraceptive pill, unprotected intercourse during the fertile period in the case of symptothermia, etc.). It should not be used as a form of contraception, or as a conventional menstruation pill, but only as a back-up solution.
It acts only by blocking ovulation. If ovulation does not take place, there is no risk of becoming pregnant, since no egg equals no fertilization. But if ovulation has already taken place and fertilization has occurred, the pill is of no use. It is therefore not an abortion pill.

There are several types of pill:

  • one with levonorgestrel, called Norlevo, which can act up to 72 hours (3 days) after unprotected or poorly protected intercourse
  • one containing ulipristal acetate, which can be taken up to 120 hours (5 days) after intercourse, known as the "morning-after pill" or Ellaone.

To improve the effectiveness of emergency contraception, the tablet should be taken as soon as possible after high-risk intercourse: within the first 12 hours. The sooner the medication is taken, the faster the contraceptive effect. The contraceptive tablet can be taken up to 72 hours after high-risk intercourse. Effectiveness ranges from 58% to 95%.
According to several studies, it would appear that the morning-after pill is more effective than the morning-after pill, since it is effective up to 5 days after unprotected intercourse.

Since it is not 100% effective, it is advisable to take a pregnancy test 2 or 3 weeks after high-risk intercourse, to ensure that it has worked properly.

How does the morning-after pill affect menstruation?

As it's a hormonal emergency contraception, it will have an impact on the body and how it functions. The morning-after pill and late periods, the morning-after pill and early periods? We explain.

Changes to the menstrual cycle

As explained above, the morning-after pill works by blocking ovulation. This obviously disrupts the various menstrual phases. As a result, since ovulation is blocked, it can be difficult to predict the date of the next ovulation and therefore the date of the next menstruation. The cycle has to be restarted to have another ovulatory phase. This upheaval has other consequences, but they're all harmless!

Some women, for example, will experience :

  • bleeding
  • nausea
  • stomach ache

Other reported effects include

  • headaches and dizziness
  • breast tension

It can be taken by anyone. There are no contraindications to taking the emergency pill, but it is not a conventional contraceptive method.

Bleeding after taking the morning-after pill

It's very common to experience bleeding after using this emergency contraceptive, so there's no need to worry. On the other hand, when your next blood loss arrives, you need to be careful that it's a real menstrual flow, and not bleeding that can also occur at the start of pregnancy. So if you have any doubts about your next period, take a pregnancy test anyway.

Premature menstruation

Bleeding may occur immediately after taking the morning-after pill. This is because the pill blocks ovulation, which by definition disrupts the hormonal cycle.
To be sure it has worked, we recommend you take a pregnancy test within 3 weeks of taking it. It does not cause premature menstruation, but rather blood loss due to the intake. However, it can delay them.

Can the morning-after pill delay menstruation?

By blocking ovulation, it modifies the cycle. Menstruation may therefore be delayed. However, if you notice a delay in your menstrual flow, it's best to take a pregnancy test to make sure you're not pregnant, as it's not 100% effective.

What should I do if my period doesn't arrive after taking the morning-after pill?

Take a pregnancy test 3 weeks after taking the pill. As explained above, it can delay menstruation, but if it still doesn't arrive, consult your doctor or gynecologist, who will be able to guide you. A blood test is also a reliable way of checking that you're not pregnant.

Whatever your situation, whether you want to get pregnant or not, remember that no one can judge your sexuality or your willingness to take contraception.

FAQs on the morning-after pill and menstruation

When do I get my period after taking the morning-after pill?

Once you've taken this emergency contraception, your cycle changes. Menstruation may therefore arrive late. However, if your period is too late, consult your health-care professional, as it could be pregnancy.

Can the morning-after pill trigger menstruation?

Yes, it can cause bleeding in the days following intake. But don't worry, this is completely normal; the body is just disturbed.

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