How Does Plan B Work?

If you’re wondering, “how does Plan B work?” you’ve come to the right place.

There are serious differences between contraception (ex. birth control pills), emergency contraception (ex. Plan B), and abortion pills (ex. Mifepristone and Misoprostol). For starters, it’s essential to understand that Plan B is classified as emergency contraception and is therefore not recommended for daily use.

In this blog, we’ll walk you through the the difference between Plan B and the Abortion Pill, and help you understand how Plan B works with your body to prevent unwanted pregnancy. 

What is the Difference Between Plan B and the Abortion Pill?

Understanding the difference between contraception, emergency contraception, and abortion pills.

  • Contraception is the term used to describe the various methods of pregnancy prevention. Examples of contraception include condoms, cervical caps, intrauterine devices, hormonal birth control pills or shots,  tubal ligation, and fertility awareness.
  • Plan B, also known as The Morning After Pill, is a form of birth control that’s only meant to be used as emergency contraception. Regular use of Plan B (as if it were similar to other hormonal birth control pills) is not recommended because it is a less effective form of birth control (when compared to other methods). Frequent use can also result in irregular periods or spotting between periods.
  • The Abortion Pill, unlike Plan B or other contraception methods, is abortion. The abortion pills Mifepristone and Misoprostol are prescription medications that terminate an early pregnancy.

Want to know more? Keep reading, as we’ll discuss how Plan B and abortion pills work throughout this article. Be sure to talk to your doctor or schedule an appointment at Pregnancy Choices to discuss the various options and methods available to you for pregnancy prevention. 

What Does Plan B Do?

Plan B was created in the late 1990s because the FDA requested an emergency contraceptive product for victims of sexual assault. Today, the morning after pill is widely used as emergency contraception after unprotected sex. Emergency contraception pills similar to Plan B include Aftera and Ella.

Plan B does NOT cause an abortion. Rather, it works by delaying or preventing ovulation. The Plan B time frame for efficacy is important to understand because it’s less likely to be effective 72 hours after unprotected sex.

Does Plan B always work? 

The short answer is, no. However, it is 89% effective at preventing pregnancy when taken in the first 72 hours. It should NOT be used as regular contraception, since it’s less effective than regular birth control methods.

Side effects of Plan B include:

  • Nausea and vomiting
  • Fatigue
  • Bleeding in between your period (spotting)
  • Cramping
  • Headaches
  • Breast tenderness

If Plan B is taken more than 72 hours after unprotected sex, it will likely have no effect — meaning you could still get pregnant. When it comes to Plan B spotting vs. implantation bleeding, implantation bleeding would happen ten to fourteen days after conception.  

What Happens If Plan B Doesn’t Work?

Signs that Plan B didn’t work include implantation bleeding or pregnancy related symptoms. In the event you’ve also missed your period after taking Plan B, you may want to follow up with your doctor or make an appointment at Pregnancy Choices to take a lab grade pregnancy test. At Pregnancy Choices, we offer free and confidential pregnancy testing as well as an optional ultrasound. Using your last menstrual period (LMP), we can also help estimate the gestational age of your pregnancy. 

How Does the Abortion Pill Work?

As we’ve stated, unlike Plan B, the Abortion Pill is a medication abortion. The Abortion Pill is also prescribed for miscarriage management; however, in this article we’ll solely be talking about its use in elective abortion. 

A medication abortion does not require any surgery or anesthesia and can be taken at home. Though the name suggests one pill, it actually consists of two medications, Mifepristone and Misoprostol. 

Mifepristone works by blocking the body’s hormone progesterone. This causes the lining of your uterus to thin, so the embryo can’t remain attached to the uterine wall.

Within 24 to 48 hours of taking the mifepristone, the second drug, misoprostol, is taken. Misoprostol causes the uterus to contract — as it would in labor—to eject the embryo from the uterus, thus terminating the pregnancy. Mifepristone is taken by mouth, but Misoprostol can be taken by mouth or inserted into the vagina.

The abortion pill is only appropriate in the first trimester because it becomes less effective later in pregnancy. In the state of Minnesota, the abortion pill is prescribed to women seeking an abortion up to 11 weeks gestation.

If you are considering a medication abortion, an ultrasound is an important step to determine how many weeks pregnant you are. An ultrasound also shows if you have an ectopic pregnancy, where the embryo is implanted outside the uterus. The abortion pill cannot be used to terminate an ectopic pregnancy.

Side effects of Mifepristone include:

  • Abdominal cramping
  • Back pain
  • Fatigue
  • Nausea
  • Headache
  • Dizziness

Misoprostol has similar side effects, including heavy bleeding, cramping, passing clots, and diarrhea. These side effects are normal, but you should contact your doctor for:

  • Bleeding that soaks more than two pads in an hour
  • Fever lasting longer than a day
  • Foul-smelling vaginal discharge
  • Severe pain in your back or abdomen
  • Your period not returning after two months
  • You’re continuing to have pregnancy symptoms

When the abortion pill is no longer safe or effective to take

The abortion pill should not be used if you’re using an intrauterine device (IUD) for birth control, if you take blood thinners, have adrenal gland problems or bleeding problems, or have an ectopic pregnancy. 

Remember — the two-step abortion pill process is most effective before 11 weeks gestation. 

What Happens When the Abortion Pill Doesn’t Work?

Should the two-Step abortion pill fail to terminate your pregnancy, you’ll need to consider:

  • Are more pills necessary to effectively terminate your pregnancy?
  • Is a surgical abortion procedure necessary?
  • Would you now like to carry your pregnancy to term?

All of these options can be sought after, and Pregnancy Choices is here to help you figure out what’s best for you.

What happens if more pills are prescribed to me?

  • If the two-step abortion pill doesn’t work, you may have to take another dose of misoprostol a week after treatment.
  • Or, you may need to undergo a surgical abortion.

What are the different surgical abortion procedures?

  • Vacuum aspiration is a procedure that uses suction to remove the embryo and the placenta from your uterus. This method is typically done up to 16 weeks gestation.
  • Dilation and evacuation are usually done after 14 weeks gestation. First, your doctor dilates your cervix so they can access the tissues in your uterus. The next day, they use forceps to take out the placenta and the fetus, suction is also used, and the lining of your uterus is scraped to ensure the pregnancy has been terminated.
  • Medical induction abortion “is mostly used after 16 weeks of pregnancy. It involves using one or more medications to start labor and delivery of the fetus. This process usually requires a hospital stay of two to three days, but the length of stay can vary.  This type of abortion is most often used in pregnancies with birth defects or pregnancy complications”.

What options are available if you choose to carry to term?

Continuing pregnancy after attempted abortion is possible, especially with options like The Abortion Pill Reversal. It’s important to attend all scheduled prenatal visits with your practitioner as well as discuss any concerns you have about your pregnancy. 

  • Adoption is an option for women who choose to carry the baby, but don’t want to parent the baby. 
  • If parenting is of interest to you, a Pregnancy Center, like Pregnancy Choices, can help set you up with car seats, sleep stations, food, formula, clothing, rental assistance and more. 

We know that having a baby can be stressful even in the best of circumstances. Our clinic provides clients with access to more than 250 community resources, ensuring you have what you need to parent successfully.

Make your decision with confidence.

An unexpected pregnancy can be life-changing news. Everyone has different feelings about pregnancy, and there is no one-size-fits-all decision. At Pregnancy Choices, our goal is to provide you with the facts so you can make an informed decision about what’s best for your life. 

Think you might be pregnant? Schedule a pregnancy test. 


All sources were reviewed by a Medical Staff Member.

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