Can You Get Pregnant after Plan B?

There are dozens of different contraceptive products available for women. While the most popular option remains the standard birth control pill, another pill has gained a lot of attention.

Plan B (levonorgestrel) is a pill that is taken the day after having unprotected sex. However, before switching birth control, you should know the pros and cons.

You need to know how effective Plan B is for preventing pregnancy and whether you can get pregnant after taking the pill.

What is Plan B?

Plan B is an emergency contraceptive. Also called the morning after pill, women can take Plan B the morning after having unprotected sex to prevent pregnancy.

The pill may significantly decrease the chances of getting pregnant. However, Plan B is not as effective as birth control pills. When used as directed, only about 1 out of 8 women that would have conceived will become pregnant.

While Plan B is not recommended as a regular form of birth control, it can offer an alternative method when other contraceptives are not available. It is often considered an emergency contraceptive.

How Does Plan B Work?

Plan B works like a regular birth control pill, with a few differences. Like birth control pills, Plan B contains a hormone called levonorgestrel. However, the Plan B pill contains a higher dose of the hormone.

The large dose of levonorgestrel that you receive from the pill reduces the risk of pregnancy in several ways. When your body receives a large dose of this hormone, it prevents the release of an egg from your ovary.

It also helps to prevent fertilization of the egg by the sperm. This hormone may also change the lining of the uterus to prevent pregnancy.

Chances of Getting Pregnant After Using Plan B

The effects of Plan B do not last long. It is recommended that you resume your normal birth control method immediately, as Plan B will not continue to protect against pregnancy. It is even possible to get pregnant within 24 hours after taking the pill, depending on your fertility factors, such as ovulation.

The pill only protects against previous incidents of unprotected sex. It can prevent pregnancy from occurring up to 120 hours after unprotected sex by preventing ovulation and transportation of the egg through the fallopian tube. As mentioned, it only works once per menstrual cycle.

For example, if you have unprotected sex on Monday and take the pill on Tuesday, there is an 89 to 95% chance that the pill will prevent successful fertilization. If you then have unprotected sex on Tuesday night, the pill will not protect against pregnancy.

It should also be noted that Plan B will not end a pregnancy. If you are already pregnant, the pill does not offer a safe solution for terminating the pregnancy.

Is Plan B Effective for Preventing Pregnancy?

The manufacturers of Plan B recommend that you use the pill as a backup option. You may use it when you make a mistake with your normal birth control method, such as forgetting to take your regular pill. You may also choose to use Plan B after a condom breaks or if you did not use a birth control method.

Plan B may be less effective if you attempt to use it a second time within the same menstrual cycle. It is only intended to be used once per cycle to protect against pregnancy.

Plan B is designed to be an effective form of birth control. However, no birth control method offers a 100% guarantee to prevent pregnancy, other than abstinence.

Can You Get Pregnant after Taking Plan B?

If you want to know whether you can get pregnant after using Plan B, the answer is yes. In fact, you could get pregnant while using Plan B. As mentioned, this pill only prevents about 7 out of 8 pregnancies that would have occurred if birth control was not taken.

The pill offers a single dose to help prevent pregnancy after having unprotected sex. When taken within 72 hours, it may reduce the chances of getting pregnant by 89%. If taken within 24 hours, you can reduce the risk of pregnancy by 95%.

Again, this pill does not stop you from getting pregnant after you take it. If you have unprotected sex after taking the pill, you may still get pregnant. The pill also does not protect against sexually transmitted diseases.

When Should You Use Plan B?

Plan B should only be used as a backup plan. You should also avoid using it frequently. It is mostly intended for use after the following scenarios:

  • You do not use birth control
  • The condom came off
  • You missed your regular birth control pills
  • Your diaphragm slipped out
  • You forgot to insert your ring

You may also take the pill if you believe that your regular birth control method did not work.

What are the Potential Side Effects of Plan B?

Plan B and the levonorgestrel hormone are considered safe for most women. The risk of side effects is minimal. However, you should consult your doctor if you experience any adverse effects, such as nausea, dizziness, or abdominal pain.

Plan B also comes with a warning that you should contact a healthcare professional if you vomit within two hours after taking the pill.

Another potential issue is a change to your menstrual cycle. While this issue is rare, Plan B may cause your next period to be lighter or heavier than usual. This change typically goes away after the next cycle.

Frequently Asked Questions

1. Will Plan B work if I’m overweight or obese?

Plan B (levonorgestrel) may be ineffective for heavier women. According to a 2011 meta-analysis, women who take levonorgestrel for emergency contraception, and have a body mass index (BMI) > 25 kg/m2, have a three times greater risk of pregnancy than women with a normal BMI.

Why is levonorgestrel less effective in high-BMI women?

In a study conducted on 10 women, investigators found that after taking levonorgestrel for emergency contraception, women with a high BMI had about half the level of the drug in their bloodstream that was found in those with normal BMIs.

Similar results were obtained by other other investigators (read more).

2. What emergency contraception is available for high-BMI women?

Levonorgestrel isn’t the only morning-after pill. Ulipristal acetate (marketed as Ella) can delay ovulation and, consequently, prevent pregnancy. While you can buy Plan over-the-counter, you will need a prescription to purchase Ella.

Ella is effective at the same level for up to five days after unprotected intercourse, unlike Plan B whose effectiveness starts to drop 72 hours after unprotected sex.

Although weight may also interfere with Ella, there isn’t enough data to support this claim. Besides, one study shows that after a single dose of emergency contraception, high-BMI women are exposed to lower concentrations of levonorgestrel and similar concentrations of ulipristal acetate when compared to normal-BMI women.

Another option that you may consider is the copper intrauterine device, which is the most effective emergency contraceptive method. The good news with this device is that it works regardless of your weight.

The bad news is that it has to be placed by a health care professional and it can cost up to $1000 if you don’t have health insurance. There are other downsides associated with the use of this device, so you should talk to your doctor before getting one.

3. What if I’m obese and Plan B is my only option?

Although Plan B may be less effective in high-BMI women, it doesn’t mean that it won’t work at all. If plan B is the only emergency contraceptive that you have access to, take it.

You should also consider talking with your ob-gyn about your birth control plan ahead of time, especially if there’s any chance you might need emergency contraception.

4. Should I double up the dose of Plan B for it to be more effective?

Although one study suggested that doubling the levonorgestrel dose may be an effective strategy to improve its efficacy in high-BMI women, there is no evidence that this makes the drug more effective. So, no, don’t take another dose. If in doubt always talk to your doctor.

5. Is it common to get cramping after taking the Plan B pill?

Yes, but if cramping is severe and persists beyond two to three days, it is important that you visit a physician because this might be a sign of an underlying problem.

There have been occasional reports of ectopic pregnancy after levonorgestrel emergency contraception. Approximately 75 percent of women with an ectopic pregnancy will present with abdominal pain, which is why you shouldn’t take severe or prolonged cramping (after taking Plan B) lightly.

Last Thoughts on Plan B and Pregnancy

Can you get pregnant after using Plan B? Yes. The pill is only effective at preventing pregnancy from a previous incident of unprotected sex. It does not stop future incidents from resulting in pregnancy.

You may even get pregnant within the next 24 hours after taking the pill. However, this will depend on whether you are ovulating and other fertility factors.

While Plan B offers an effectiveness between 89 and 95%, it is not intended as a regular form of birth control. Women are encouraged to use it as a backup plan when they forget to take one of their regular pills or when other birth control methods, such as condoms, do not work.

Medical disclaimer: The authors of this website are not medical professionals, and all of the material on this Site (including: text, images, graphics, outcomes, charts, messages and any other material) are for informational purposes only and are not a substitute for professional medical advice, diagnosis or treatment. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects, nor should it be interpreted to indicate that use of any drug is safe, appropriate or effective for you or anyone else. Always consult your doctor, physician or other licensed healthcare provider before taking any drug, making modifications to your diet, starting or discontinuing your treatment, or with any questions or concerns you have regarding your health. Never ignore or disregard medical advice or delay seeking medical advice because of something you read on this Site. Reliance on any material provided on the Site is solely at your own risk. Any application of the material provided is at your own risk and is your sole responsibility.

Further Reading

  1. Kitani Y, Ishiguro T, Kobayashi A, Tamura R, Ueda H, Adachi S, Nishikawa N, Sekine M, Enomoto T. Ectopic pregnancy following oral levonorgestrel emergency contraception use. J Obstet Gynaecol Res. 2018 Sep 23. doi: 10.1111/jog.13815. Read the article.
  2. Festin MP, Peregoudov A, Seuc A, Kiarie J, Temmerman M. Effect of BMI and body weight on pregnancy rates with LNG as emergency contraception: analysis of four WHO HRP studies. Contraception. 2017 Jan;95(1):50-54. doi: 10.1016/j.contraception.2016.08.001. Read the article.
  3. Praditpan P, Hamouie A, Basaraba CN, Nandakumar R, Cremers S, Davis AR, Westhoff CL. Pharmacokinetics of levonorgestrel and ulipristal acetate emergency contraception in women with normal and obese body mass index. Contraception. 2017 May;95(5):464-469. doi: 10.1016/j.contraception.2017.01.004. Read the article.
  4. Stone R, Rafie S, El-Ibiary SY, Vernon V, Lodise NM. Emergency Contraception Algorithm and Guide for Clinicians. Nurs Womens Health. 2017 Aug – Sep;21(4):297-305. doi: 10.1016/j.nwh.2017.06.005. Read the article.
  5. Edelman AB, Cherala G, Blue SW, Erikson DW, Jensen JT. Impact of obesity on the pharmacokinetics of levonorgestrel-based emergency contraception: single and double dosing. Contraception. 2016 Jul;94(1):52-7. doi: 10.1016/j.contraception.2016.03.006. Read the article
  6. Kapp N, Abitbol JL, Mathé H, Scherrer B, Guillard H, Gainer E, Ulmann A. Effect of body weight and BMI on the efficacy of levonorgestrel emergency contraception. Contraception. 2015 Feb;91(2):97-104. doi: 10.1016/j.contraception.2014.11.001. Read the article.
  7. Munro ML, Dulin AC, Kuzma E. History, policy and nursing practice implications of the plan b(®) emergency contraceptive. Nurs Womens Health. 2015 Apr-May;19(2):142-53. doi: 10.1111/1751-486X.12186. Read the article.
  8. Eggertson L. Plan B emergency contraceptive may be ineffective for heavier women. CMAJ. 2014 Jan 7;186(1):E21-2. doi: 10.1503/cmaj.109-4671. Read the article.
  9. Plan B One-Step OTC. Med Lett Drugs Ther. 2013 Jun 24;55(1419):52. Read the article.
  10. Glasier A, Cameron ST, Blithe D, Scherrer B, Mathe H, Levy D, Gainer E, Ulmann A. Can we identify women at risk of pregnancy despite using emergency contraception? Data from randomized trials of ulipristal acetate and levonorgestrel. Contraception. 2011 Oct;84(4):363-7. doi: 10.1016/j.contraception.2011.02.009. Read the article.

I’m Princila, founder of Check Ovulation and a proud mom of two. I’m an alumna of James Lind Institute. After working in clinical jobs, my passion for writing took its toll, and I ended up switching careers to work in the medical publishing industry. I also have a passion for healthy food, which prompted me to take several online courses in nutrition and health offered by Wageningen University. (I still haven’t completed the courses thanks to my busy mommy schedule!). When I’m not writing/editing scientific and medical manuscripts or taking care of my family, I use my free time to research, learn, and write about healthy living. I have also authored a few books in the self-help niche using the pen names Princila Murrell or PN Murray. Protection Status