Will Taking Plan B Cause a Miscarriage?

Plan B won't cause you to miscarry, but it can help prevent pregnancy

woman with pill and water in hand
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If you are intimate and do not use protection, forget to take oral contraceptives, or your preventative measures do not work as planned, you may be concerned about getting pregnant. When it comes to avoiding pregnancy, in the case of immediately failed contraception, Plan B may be an option.

What Is Plan B?

Plan B is a type of emergency contraception. When taken within a few days of unprotected sex, before you or your partner is technically pregnant, emergency contraception can reduce the odds a pregnancy will occur.

Plan B works in one of three ways. The Plan B pill must be taken within 72 hours of having unprotected sex. For the pill to be most effective, it should be taken within 12 hours. When taking Plan B, you only have to take one dose. Purchasing multiple pills does not increase the pill's efficacy.

One way Plan B terminates a pregnancy is by stopping your ovary from releasing an egg. Plan B can also prevent fertilization; should an egg be in the early stages of fertilization, Plan B can stop the egg from embedding itself into your uterus.

Plan B is not recommended for women above 175 pounds and may be less effective for those above 165 pounds as well. Other drugs, including anticonvulsant drugs, antibiotics, rifampicin, rifabutin, griseofulvin, and St. John’s wort, can also make Plan B less effective. Plan B should not be taken if you have abnormal vaginal bleeding or may be allergic to any of the pill's ingredients.

Can Plan B Terminate a Pregnancy?

While Plan B can help prevent an unwanted pregnancy, Plan B will not cause an abortion or induce a miscarriage. By the time it is possible to confirm that you are pregnant (as you get a positive result on an at home pregnancy test), implantation has already taken place and taking Plan B will not have any effect.

Although there are prescription-only drugs that can terminate a pregnancy, Plan B does not fall into that category. If you are currently dealing with an unplanned pregnancy, speak with a gynecologist or family planning physician about your other options.

Side Effects of Plan B

Most women who take Plan B do not experience any side effects. Of those who do, side effects may include:

  • Nausea 
  • Vomiting 
  • Abdominal pain
  • Dizziness
  • Fatigue 
  • Headache 

If you experience nausea and vomiting within two hours of taking Plan B, you might not have absorbed the dose and may need a second. If this occurs, call your doctor or speak to a pharmacist to get their advice. Side effects typically pass within 24 hours. In most cases, your period will come on time, but it is possible for it to come early or late or for you to experience breakthrough bleeding. 

Plan B should not be used as regular contraception. If you are looking for a long-term contraception option, speak with your physician about the different options available.

View Article Sources
  • Plan B Emergency Contraception. McKinley Health Center.
  • Plan B Dosage Guide and Information. 2017.