Even if you’re using protection, there’s always a chance that you could get pregnant. Perhaps you’ve turned to Plan B to avoid an unplanned pregnancy. But, what happens if Plan B fails? It’s crucial to understand your pregnancy options so you can plan your next steps!

Today, we’re discussing Plan B—including how it works, the risks and side effects, and what to do if you still get pregnant after taking it. Keep reading to learn more!

How Does Plan B Work?

Plan B is a form of emergency contraception that lowers the risk of pregnancy by preventing or delaying ovulation. It’s often used when birth control fails or in cases of sexual assault.

However, Plan B doesn’t always prevent ovulation,[1][2][3] but may also work by disrupting the hormonal environment and interfering with the embryo’s attachment to the uterus, resulting in its death.[4]

It’s important to know that Plan B and all other forms of emergency contraception should only be used as backups, not as primary methods of birth control.[5]

Is Plan B an Abortion Pill?

While they seem similar, Plan B and the abortion pill are not the same things. The difference is that Plan B aims to keep you from getting pregnant in the first place and may disrupt a newly formed embryo from continuing to grow[6], but the abortion pill is designed to end a pregnancy every single time it is used.

If you have been sexually active in weeks prior to taking Plan B you may want to take a pregnancy test or even receive an ultrasound just to be certain that you’re not pregnant from a previous sexual encounter.

Can Plan B Cause Miscarriage?

A miscarriage is an unintended loss of a pregnancy before the 20th week of pregnancy. While the goal of Plan B is to prevent pregnancy altogether, if an embryo has already formed when Plan B is taken, it may interfere with the embryo’s ability to attach to the uterus, resulting in its death.[7] If that is not your intent, then Plan B may not be for you.

How Effective is Plan B? When Can I Take Plan B?

Plan B is most effective when taken as soon as possible after having unprotected sex. It is reported to reduce the risk of pregnancy for up to 72 hours, but is not always effective.[8]

Plan B can be less effective for women who take certain medications (such as St. John’s wort or barbiturates) or for women who are overweight.[9]

Does Plan B Have Side Effects?

Common side effects of Plan B include[10]:

• Dizziness
• Headache
• Cramps or abdominal pain
• Nausea or vomiting
• Breast tenderness
• Delayed period, irregular bleeding, and/or heavier bleeding during your next period[11]

These side effects should be mild and only last a few days. However, if you experience bleeding or spotting for longer than a week or have significant lower abdominal pain after taking Plan B, contact your healthcare provider immediately, as these symptoms can indicate a miscarriage or ectopic pregnancy has occurred.[12]

Does Plan B Have Risks?

Plan B should not be used as routine birth control and could alter or delay your menstrual cycle. Further, Plan B does not protect against sexually transmitted infections.[13]

What to Do if Plan B Fails

Even when used correctly, Plan B may occasionally fail. If you’ve taken Plan B and missed your period, it could mean that you’re pregnant.[14]

If your results come back positive, don’t panic. Our compassionate team is here to help you explore all of your pregnancy options so that you can make an informed and empowered decision! We will do everything we can to equip you to take your next steps with confidence!

Give us a call at 320-253-1962 or make an appointment online today. All services are confidential and free of charge!

Please be aware that Pregnancy Resource Center + Medical Clinic does not provide or refer for abortion services.

Sources

1. Hapangama D, Glasier AF, Baird DT. “The effects of peri-ovulatory administration of levonorgestrel on the menstrual cycle.” Contraception. 2001 Mar;63(3):123-9. DOI:10.1016/s0010-7824(01)00186-x https://www.contraceptionjournal.org/article/S0010-7824(01)00186-X/fulltext
2. Croxatto, HB, Brache V, Pavez M, Cochon L, Forcelledo ML, Alverez F, Massai R, Faundes A, and Salvatierra AM, 2004. “Pituitary-ovarian Function Following a Standard Levonorgestrel in Emergency Contraception Dose or a Single 0.75 mg Dose Given on the Days Preceding Ovulation.” Contraception. 2004 Dec;70(6):442-50. DOI:10.1016/j.contraception.2004.05.007 https://www.contraceptionjournal.org/article/S0010-7824(04)00156-8/fulltext
3. AAPLOG Committee Opinion #7. (2020, January). Embryocidal Potential of Modern Contraceptives. https://aaplog.org/wp-content/uploads/2024/05/Committee-Opinion-7-updated.pdf
4. See #3.
5. Levonorgestrel (Oral Route) Side Effects. Mayo Clinic. (2024, September 1). https://www.mayoclinic.org/drugs-supplements/levonorgestrel-oral-route/side-effects/drg-20074413
6. Kahlenborn, C., Peck, R., & Severs, W. B. (2015). Mechanism of action of Levonorgestrel emergency contraception. The Linacre Quarterly, 82(1), 18-33. https://doi.org/10.1179/2050854914y.0000000026
7. See source #6.
8. See source #5.
9. Mayo Foundation for Medical Education and Research. (2022, June 3). Morning-after pill. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/morning-after-pill/about/pac-20394730#
10. See source #9.
11. See sources #5 and #9.
12. See sources #5 and #9.
13. See source #9.
14. See sources #5 and #9.