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

Written by Marion Goilav Professional proofreading
Reviewed by Charline midwife Professional proofreading


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 periods ? 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 emergency contraception 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 contraceptive, or as a conventional periods pill, but only as a back-up solution.
It acts only by blocking ovulation. If ovulation does not occur, there is no risk of becoming pregnant, since no egg equals no fertilization. However, 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 sexual intercourse
  • one with ulipristal acetate, which can be taken up to 120 hours (within 5 days) afterwards, 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 smake sure it has worked.

What are the effects of the morning-after pill on periods ?

As it is a hormone-based emergency contraception, it will have an impact on the body and how it functions. The morning-after pill and periods 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 it 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 have :

  • bleeding
  • nausea
  • stomach pains

Other effects reported include:

  • headaches and dizziness
  • breast tension

It can be given to 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 lemergency contraception, so there's no need to worry. On the other hand, when your next blood loss occurs, you need to make sure 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 periods : take a pregnancy test anyway.

The premature arrival of periods

Immediately after taking the morning-after pill, bleeding may occur. This is because it blocks ovulation, which, by definition, disrupts the hormonal cycle.
To be sure it has worked, it is advisable to 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 the arrival of periods ?

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 to do if periods does not arrive after taking a morning-after pill?

Take a pregnancy test 3 weeks after intake. 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 use contraception.

FAQs on the morning-after pill and periods

When do periods arrive after taking the morning-after pill?

After taking this emergency contraception, the cycle changes. Menstruation may therefore be late. However, if your period is too late, consult your health care professional, as it could sbe a pregnancy.

Can the morning-after pill trigger periods ?

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


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