Does the morning after pill affect your fertility?

At a glance: The morning after pill is a useful method to avoid unwanted pregnancies. Despite common misconceptions, there is no scientific evidence that its use has any effect on women’s fertility.

What is the morning after pill?

Morning after pills are a form of hormonal emergency contraception. No matter what contraception method you choose, sometimes life happens and you might find yourself in need of a backup plan. Whether you've had unprotected sex, accidentally forgot to take the pill, or the condom ripped; emergency contraception can be a valuable tool to avoid unwanted pregnancies.

Although the morning after pill has proven to be beneficial for women's reproductive health and rights, there are widely spread myths and misconceptions about how it works and what effects it might have on fertility. In this blog, we will address these worries together. Let’s start from science.

Is there more than one morning after pill?

Yes. If you ask for it at the pharmacy, you can find two kinds of emergency contraception pills: levonorgestrel and ulipristal acetate. You might know the latter as ellaOne, its commercial name. Both are effective, but they differ in mechanism and time window of their action (so, the amount of time there can be between having sex and taking the pill).

How do they work?

What can they do?

Both kinds of pills act by delaying or preventing ovulation (the moment when the egg leaves the ovary), so that the sperm cannot find an egg to fertilize. This is how they prevent you from getting pregnant. It's important to take the pills as soon as possible after having sex, since their effectiveness declines over time (reference 1, 3). In other words, if you are leaving for a weekend outside town after unprotected sex, it is best to stop by at the pharmacy before leaving.

How do they do it?

The key element for the mechanism of both pills is the hormone progesterone. Progesterone prevents pregnancy by inhibiting ovulation and thickening cervical mucus. In this condition, the egg is not able to be fertilized and to implant. Although their effects are similar, there are some differences between the two pills.

Levonorgestrel is a synthetic (man-made) form of the hormone progesterone. It is effective within 72 hours from when you have sex. The efficacy of Levonorgestrel in preventing pregnancy is estimated between 97.4 and 99.4%, if taken within 72 hours (reference 1 and 3).

Ulipristal acetate (ellaOne) is a selective progesterone receptor modulator - wait, what? This means that it acts by regulating the cellular response to the hormone progesterone, with similar effects to the ones of levonorgestrel. Just like with levonorgestrel, the sooner its taken, the more effective it is, but Ulipristal acetate has a longer effective time window of 120 hours (5 days) after sex. The estimated efficacy of ulipristal acetate is between 98 and 99%, if taken within 120 hours (reference 1 and 3). If you forgot to take the morning after pill for more than 72 hours after you had sex, ulipristal acetate can still help you!

What can’t they do?

If the ovulation has already occurred, these pills cannot prevent a possible pregnancy. If the egg has already left the ovary, they can’t delay it any further, and your egg will be available to be fertilized.

You might have heard people comparing morning after pills to abortion pills, so let’s clarify that misunderstanding. Morning after pills are not abortion pills; they can’t stop a pregnancy if the egg has been fertilized, meaning they cannot induce abortion.

What happens after you take the morning after pill? Are you protected if you have unprotected sex again?

Taking oral emergency contraception does not prevent future pregnancy and does not protect from STDs. They cannot act as contraception in case of unprotected sex after you take them (reference 1). It is important to remember that the morning after pill is useful for what happened yesterday, but it cannot do anything for the future.

Do they affect my fertility?

No, they don’t. Many women fear that taking a morning after pill (or taking it more than once) might have long-term effects on their fertility. Fortunately, you have nothing to be worried about. Using morning after pills does not have long-term effects on your fertility or general health. There is also no evidence that taking these pills multiple times will increase the risk of long-term side effects (reference 1, 2, 3, 4, 5).

Possible short-term side effects

"Ok, cool. But I took it once and I didn’t feel great at all." This can happen, but it is just a temporary effect. About 1 in 10 women experience short-term side effects. The most common ones are headaches, stomach pains, breast tenderness, dysmenorrhea (menstrual pain), mood swings, nausea and vomiting (reference 2, 3, 4). None of these symptoms are an indication of long-term effects due to the use of emergency contraception. Your next cycle might be irregular, due to the emergency contraception. However, this effect is only temporary, and does not affect the regularity of your later cycles.

Do I have to change when I take my birth control pill if I use emergency contraception?

Does your regular hormonal control pill contain progestins? If so, this paragraph is for you! So you forgot to take your regular pill, had unprotected sex, and now you need an emergency contraception pill. Is one better than the other? What'll happen to your usual hormonal birth control pill? In this case, it's important to consider what emergency contraception you're taking. If you take levonorgestrel, it is suggested to take your next regular birth control progestogen pill within 12 hours from the emergency contraception, and to keep on taking it regularly afterwards (reference 2,3). However, if you take ulipristal acetate (ellaOne), the progestogen in your regular birth control pill might interfere with the emergency contraception. In this case, it is recommended to wait 5 days after taking ulipristal acetate to restart your regular birth control pill (reference 2,3). Before restarting the regular contraceptive pill, other barrier methods of contraception (condoms or diaphragm) can be used to avoid pregnancy.

Can anyone take oral emergency contraception?

In some cases, you might be advised not to take oral emergency contraception. For instance, if you've experienced ectopic pregnancy, if you have severe liver dysfunction, severe asthma, or if you are taking certain medicinal products. You should pay particular attention and refer to your GP if you are taking medical drugs such as: the herbal medicine St John's Wort; some medicines used to treat epilepsy, HIV or tuberculosis; medicine that reduce your stomach acidity (for instance omeprazole); some antibiotics (rifampicin and rifabutin). These drugs can significantly reduce the effect of emergency contraception (reference 2, 3). As explained above, the use of birth control pills with progestins can also interfere with the effectiveness of ulipristal acetate (ellaOne).

In summary, the timeframe of when you can use the morning after pill is not limited to the day after intercourse. There's a longer time of efficacy that varies depending on what pill you use.

In any case, it is recommended to take them as soon as possible, since their effectiveness declines over time. Both kinds of pills only work if the ovulation has not happened yet, and they cannot interrupt a pregnancy.

Although you might experience some short-term side effects, there is no evidence that the use of (multiple) emergency contraception will affect your health or fertility in the long-term.

In some cases (if you are taking other drugs, the progestin birth control pill, or if you suffer from severe asthma or severe liver dysfunction), you might want to contact your GP and discuss the best emergency contraception method for you.


  1. Celia M. J. Matyanga, Blessing Dzingirai, "Clinical Pharmacology of Hormonal Emergency Contraceptive Pills", International Journal of Reproductive Medicine, vol. 2018, Article ID 2785839, 5 pages, 2018.


  3. Emergency Contraception March 2017 (Amended December 2020), Faculty of Sexual & Reproductive Healthcare