Can Taking Plan B® Affect Fertility?

By Halle Tecco, MBA, MPH

If you have taken Plan B®, or another brand of emergency contraception, you are not alone. More than one third of women aged 15-34 (including myself!) have taken emergency contraception to prevent pregnancy. [1] There is so much misinformation out there about Plan B®, not least of which is around how it impacts fertility. In this article, we’ll dive into the FACTS. 

But if you’re worried, know this: Plan B® does not negatively impact future fertility. [2] 

What is emergency contraception?

Emergency contraception is a way to prevent pregnancy after unprotected intercourse or a contraceptive failure. There are two types of emergency contraception:

1. Emergency contraceptive pills

Also known as the “morning-after pill.” These can include: [3]

• Pills containing levonorgestrel, often sold under the brand name Plan B®. We’ll focus mostly on levonorgestrel in this article. 
• Pills containing ulipristal acetate (brand name Ella®) which is a progestin-only pill that delays ovulation so that any sperm cannot find an egg to fertilize and so no pregnancy can occur.
• Combined oral contraceptive pills (COCs) contain both estrogen and progestin to prevent ovulation. 

2. Copper intrauterine device (IUD) 

The copper IUD is a small, T-shaped device that is inserted into the uterus by a healthcare provider. [4] It can be inserted up to five days after unprotected intercourse and can prevent pregnancy by creating an environment that is hostile to sperm, preventing fertilization. [4] The copper IUD can also act as a form of long-term birth control, with a typical use effectiveness rate of over 99%. [4]

So how does emergency contraception work?

Plan B®, also known as the "morning-after pill," is a form of emergency contraceptive (that first bucket above) which can be used to prevent pregnancy after unprotected sex. It works by temporarily delaying the release of an egg from the ovary. [5]

Similar to many combination birth control pills, it contains the hormone levonorgestrel, which is part of a class of medications called progestins. [5] The way it works is simple: it prevents the egg from being released. [5] No egg = no pregnancy. 

It's important to note that levonorgestrel is not effective if you are already pregnant, and it should not be used as a regular form of birth control. [5]

How effective is it?

Emergency contraception can significantly reduce the risk of pregnancy. The effectiveness of levonorgestrel varies depending on a number of factors, including when it is taken in relation to unprotected intercourse. The sooner it is taken, the more effective it will be at preventing pregnancy.

Plan B® (and any other brand of levonorgestrel) has been shown to be 87% to 90% effective at preventing pregnancy when taken within 72 hours of unprotected sex. [6] That percent goes down to 72% to 87% when taken between 72 and 120 hours. [6] This means that about one out of 10 women who take emergency contraception within three days will still become pregnant (and about nine will not). It’s also important to note that Plan B and other levonorgestrel pills are less effective for those who weigh over 165 lbs. [7]

It's important to remember that levonorgestrel is not a substitute for regular birth control methods, and it is certainly not as effective as, say, an IUD. It should be used only in emergency situations and not as a regular method of birth control. [5,7]

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Is Plan B® an abortion pill?

There’s a lot of misinformation and misunderstanding out there about emergency contraceptives like Plan B®. One misleading myth is that Plan B® is an abortion, which is simply not true. 

Think about levonorgestrel more like pregnancy prevention: it works by preventing ovulation, thickening cervical mucus, and thinning the lining of the uterus. [5] It can help prevent pregnancy by making it difficult for sperm to fertilize an egg or by making it less likely for a fertilized egg to implant and begin to grow.

Abortion pills on the other hand, are used to end a pregnancy after it has begun. Abortion pills, like mifepristone and misoprostol, are effective 95-99% of the time and work by blocking the hormones that are necessary for a pregnancy to continue. [8]

How long does the morning after pill take to work?

The hormone levonorgestrel gets to work quickly. In fact, research has shown that circulating levels peak about 1.7 hours after taking the pill. [5] The sooner you take it after unprotected sex, the better.

Does emergency contraception affect fertility?

Despite the fact that one survey showed that 40% of people believe the morning after pill can make you infertile if you use it too many times…there is currently no evidence to suggest that taking levonorgestrel affects your fertility in the long-term. [2]

Also, emergency contraception will not affect future pregnancies. Even if you take levonorgestrel many times, there is no evidence that it leads to infertility, miscarriage, or stillbirth. [2]

Trying to conceive after the morning after pill

There is no delay in the return to fertility after taking emergency contraception pills like levonorgestrel. [9] You will likely have a significant change in your period the cycle you take levonorgestrel, but studies show that it usually goes back to normal in the next cycle and beyond. [2]

That being said, many people struggle to get pregnant (1 in 5). [9] And many people take emergency contraception like levonorgestrel (1 in 3). [1] If you fall into both of these groups, know that it’s unlikely to be correlated. 

Still, getting a negative pregnancy test, month over month, can feel so defeating. And you may be looking for answers to why. About one-third of infertility cases are attributed to male factors and one-third to female factors. For the remaining one-third of infertile couples, the cause is a combination of problems in both partners or, in about 20% of cases, it is unexplained. [10]

A healthy lifestyle is vitally important when you’re trying to get pregnant, and certain habits can harm your fertility (we’ve gone over these more in depth in this article). These include:

• Weight outside the healthy range for your height. Being either underweight or overweight can inhibit the body from conceiving because it can disrupt the body’s natural ovulation cycle. [11] 
• Untreated sexually transmitted infections (STIs). Some STIs, like gonorrhea and chlamydia, can cause scarring in the fallopian tubes, which prevents the egg from traveling down to be fertilized by sperm. [12]
• Cigarette smoking. Smoking cigarettes makes conception less likely, as it can harm the natural hormone cycle that regulates reproductive systems [13]. It also increases the risk of miscarriage significantly. [14]

And these habits aren’t just important for you, it’s also vitally important for sperm health. Remember, male factor is a contributing cause of a couple’s infertility in about 30-40% of couples. [15]

Chances of getting pregnant by age

One 2017 study on age and fecundability (the probability of conceiving during a menstrual cycle) looked at the time to pregnancy for couples with no history of female or male infertility, who were not using any fertility treatments or medications to get pregnant. [16] This is what they found:

As you can see, age does impact the chances of conceiving. This study did not include the chances for those with a history of infertility or those utilizing fertility treatments, so your individual chances could vary greatly from this data. [16] There are a lot of options, like ovulation induction medications, IVF and IUI that you may be able to pursue if you want to increase your chances of getting pregnant now or in the future. 

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Summing it up

Plan B® is a brand of emergency contraception (the generic name is levonorgestrel) that is quite effective at preventing pregnancy. While more than one third of women ages 15-34 have taken emergency contraception, there is still a misunderstanding that emergency contraception negatively impacts fertility. [1] However, levonorgestrel is deemed safe, and there’s no evidence to suggest it can harm fertility or impact future pregnancies. [5] While it may impact the timing of the menstrual cycle when you take it, the next period should go back to normal and your fertility should resume. [2,5]

If you are having difficulties getting pregnant, and have taken emergency contraception in the past, know that these two things are not correlated. Infertility impacts 1 in 5 couples and may have happened either way. [9] But infertility does not mean that you can’t get pregnant. It just means that it may take longer, and it might take some medical intervention.

References:

1. Emergency Contraception, KFF, August 04 2022. URL. Accessed March 2023.
2. Endler M, Li R, Gemzell Danielsson K. Effect of levonorgestrel emergency contraception on implantation and fertility: A review. Contraception. 2022;109:8-18. doi:10.1016/j.contraception.2022.01.006
3. Emergency Contraception. WHO. 9 November 2021. URL. Accessed March 2023.
4. Lanzola EL, Ketvertis K. Intrauterine Device. [Updated 2022 Jul 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
5. Matyanga CMJ, Dzingirai B. Clinical Pharmacology of Hormonal Emergency Contraceptive Pills. Int J Reprod Med. 2018;2018:2785839. Published 2018 Oct 4. doi:10.1155/2018/2785839
6. Rodrigues I, Grou F, Joly J. Effectiveness of emergency contraceptive pills between 72 and 120 hours after unprotected sexual intercourse. Am J Obstet Gynecol. 2001;184(4):531-537. doi:10.1067/mob.2001.111102
7. Which kind of emergency contraception should I use? Planned Parenthood. Accessed March 2023. URL. 
8. The Facts on Mifepristone. Planned Parenthood. October 2019. URL. 
9. Infertility FAQs. Centers for Disease Control and Prevention. Last Reviewed: March 10, 2023. URL. Accessed March 2023.
10. What Causes Infertility? American Society for Reproductive Medicine. Accessed March 2023. URL. 
11. Weight and Fertility. American Society for Reproductive Medicine. Revised 2015. URL. Accessed March 2023. 
12. Tsevat DG, Wiesenfeld HC, Parks C, Peipert JF. Sexually transmitted diseases and infertility. Am J Obstet Gynecol. 2017;216(1):1-9. doi:10.1016/j.ajog.2016.08.008
13. Marom-Haham L, Shulman A. Cigarette smoking and hormones. Curr Opin Obstet Gynecol. 2016;28(4):230-235. doi:10.1097/GCO.0000000000000283
14. Pineles BL, Park E, Samet JM. Systematic review and meta-analysis of miscarriage and maternal exposure to tobacco smoke during pregnancy. Am J Epidemiol. 2014;179(7):807-823. doi:10.1093/aje/kwt334
15. Practice Committee of the American Society for Reproductive Medicine. Diagnostic evaluation of the infertile male: a committee opinion. Fertil Steril. 2015;103(3):e18-e25. doi:10.1016/j.fertnstert.2014.12.103
16. Wesselink AK, Rothman KJ, Hatch EE, Mikkelsen EM, Sørensen HT, Wise LA. Age and fecundability in a North American preconception cohort study. Am J Obstet Gynecol. 2017;217(6):667.e1-667.e8. doi:10.1016/j.ajog.2017.09.002