The Morning After Pill – What You Need to Know 

You had unprotected sex and now you’re worried you might be pregnant. You’ve heard that the Morning After Pill – or Plan B – can prevent you from getting pregnant, but you’re not exactly sure what it is or how it works. That’s okay.

At NAME OF CENTER, we know things don’t always go as planned. That’s why we want you to have the facts about this drug before you decide if it’s right for you. We also offer confidential consultations to help you explore your options and any risk factors associated with the pill so you can make an informed choice.

What It Is

The morning after pill is considered a type of emergency contraception that is taken within 72 hours of having unprotected sex to help prevent pregnancy. Women usually think about using the morning after pill if they didn’t use birth control, missed taking a birth control pill, their method of birth control failed, or they were sexually assaulted.

There are two types of the pill.

  • One contains levonorgestrel (marketed primarily as Plan B One StepTM) and is available over the counter for anyone over 17.
  • The other contains ulipristal acetate (marketed primarily as EllaTM) and is available by prescription only.

What It Isn’t

  • Plan B is not a primary method of birth control. It is intended for one-time use only1.
  • The morning after pill also is not RU-486, the abortion pill, that combines mifepristone with misoprostol to terminate a viable pregnancy — one in which the embryo has attached to the uterine wall and has begun to develop2.

How It Works

The over-the-counter pill uses a high dose of the progestin hormone levonorgestrel (LNG), which is used in lower doses in many birth-control pills. It must be taken as soon as possible after having unprotected sex, but no later than 72 hours3.

The prescription pill option contains ulipristal acetate (UPA), a non-hormonal drug that is meant to block the effects of key hormones necessary for conception. The primary difference between UPA and LNG is the length of time you have to take it – up to 120 hours, or 5 days, after unprotected sex4.

Depending on where you are in your menstrual cycle, both forms of the pill work in one of three ways to potentially prevent a viable pregnancy:

  • Prevents the release of an egg (ovulation) during your menstrual cycle
  • Makes vaginal fluid thicker to help prevent sperm from reaching an egg (fertilization)
  • Changes the lining of the uterus to stop attachment of an embryo5.

Its Effectiveness

Almost no drug is 100% effective. The morning after pill is no different. Based on the data scientists have, one-dose emergency contraception pills are effective at preventing pregnancy between 50-100% of the time6. There’s such a wide range of effectiveness because results are difficult to study. For example, women don’t get pregnant every time they have unprotected sex, so it’s hard to know if a pregnancy was actually prevented by taking the pill or if a woman wouldn’t have gotten pregnant anyway. Pharmaceutical companies that produce the pill report an average effectiveness of 87% for LNG and 85% for UPA7, giving you a 1 in 8 chance of still getting pregnant.

While the morning after pill is considered more effective the sooner you take it after having unprotected sex, there are several things that studies show can make it less effective or completely ineffective.

  • Timing – if you have already ovulated or have started ovulating at the time of sexual intercourse, neither pill will prevent pregnancy. They could, on the other hand, prevent an embryo from attaching to your uterus8. This is where an ethical dilemma is raised for many, as embryologists agree that a unique life begins at conception – or fertilization9 – and preventing an embryo from attaching to the uterus is considered early abortion by many.
  • BMI – your body mass index can affect how well the pill works. People who have a BMI of 30 or higher, or who weigh more than 165 pounds, have pregnancy rates that are 2 to 4 times higher when taking emergency contraception than those with a BMI of 25 or less10.
  • Drug Interactions – the labels on the morning after pill make it clear that there are a number of drugs that can interfere with the pills’ effectiveness, including barbiturates, certain seizure medications, some antibiotics, St. John’s wort, and others11.

What It Can’t Do

It’s also important that you understand what the morning after pill can’t do so you aren’t taken by surprise. It can’t12:

  • Reverse or abort a pregnancy that has already begun (the embryo has fully implanted in the uterus to begin a viable pregnancy)
  • Protect against HIV (AIDS) and other sexually transmitted diseases (STDs)
  • Protect against pregnancy if you have unprotected sex again after taking it
  • Be used as a regular form of contraception
  • Abort an embryo growing in the fallopian tube (ectopic pregnancy)
  • Guarantee that you will not get pregnant

Side Effects & Risk Factors

Potential side effects of the morning after pill include13:

  • nausea
  • abdominal pain
  • fatigue
  • headache
  • menstrual changes
  • dizziness
  • breast tenderness
  • vomiting

Some of these symptoms can mimic those of an ectopic pregnancy, which requires emergency care. Also, levonorgestrel may cause unexpected bleeding. If it doesn’t go away by your next period, you may need to get a pregnancy test to determine if you’re pregnant. LNG may also cause your period to come earlier or later. Because of this, you may be more susceptible to pregnancy during that time if having unprotected sex14.

The UPA pill comes with a warning, as well. If you normally use a birth control pill that contains progestin, you should not take the birth control for 5 days after taking this morning after pill. If you do, the effectiveness of the UPA can be significantly impaired15. Having unprotected sex during those days can increase your risk of pregnancy.

Before You Decide – We Can Help

Taking any drug is an important decision. Before you take the morning after pill, you should weigh the risks and identify any complicating factors you may have. At a minimum, you should:

  • Get a pregnancy test
  • Be tested for STDs
  • Identify risk factors you have for the pill’s effectiveness
  • Explore any ethical concerns the pill may pose for you
  • Have your questions answered

Contact Us Today at ____________.

WERE YOU SEXUALLY ASSAULTED? If you are seeking the morning after pill because you were sexually assaulted, call law enforcement immediately to report the incident or go to your nearest emergency room for help. Then, come to NAME OF CENTER for support.

While NAME OF CENTER does not provide the morning after pill or refer for it, we are committed to helping you get the information you need to make an informed decision and to supporting you no matter what you choose.



1 Mayo Clinic. (2021, March). Levonorgestrel (Oral Route) Precautions – Mayo Clinic.

2 Utah Department of Health. (Accessed 2021, March). Abortion Procedures – Utah Department of Health.

3 Plan B FAQs | Plan B One-Step®. (n.d.). Foundation Consumer Healthcare. Retrieved March 2021, from

4 Fine P, Mathé H, Ginde S, Cullins V, Morfesis J, Gainer E. Ulipristal acetate taken 48–120 hours after intercourse for emergency contraception. Obstetrics & Gynecology. 2010;115(2, Part 1):257–63.

5 U.S. Food and Drug Administration. (2015, December 7). FDA’s Decision Regarding Plan B: Questions and Answers. U.S. Food and Drug Administration.,Plan%20B%20will%20not%20work

6 Trussel, J., Raymond, G., & Cleland, K. (2019, January). Emergency contraception: a last chance to prevent unintended pregnancy. Princeton University.

7 Duramed Pharmaceuticals Inc. (2009) Plan B One-Step prescribing information. Duramed Pharmaceuticals, Inc.

8 Peck, R., Rella, W., Tudela, J., Aznar, J., & Mozzanega, B. (2016). Does Levonorgestrel Emergency Contraceptive have a Post-Fertilization Effect? A Review of its Mechanism of Action. The Linacre Quarterly83(1), 35–51.

9 Oliver, R. (2020, July 10). Embryology, Fertilization – StatPearls – NCBI Bookshelf. National Center for Biotechnology Information.

10 Glasier A, Cameron ST, Blithe D, Scherrer B, Mathe H, Levy D, et al. Can we identify women at risk of pregnancy despite using emergency contraception? Data from randomized trials of ulipristal acetate and levonorgestrel. Contraception. 2011Oct1;84(4):363–7.

11 Duramed Pharmaceuticals Inc. (2009) Plan B One-Step prescribing information. Duramed Pharmaceuticals, Inc.

12  Ibid

13 Morning-after pill – Mayo Clinic. (2020, June 19). Mayo Clinic.

14 Stuart, A. (2010, May 4). Levonorgestrel Emergency Contraception. WebMD.

15 Kim A, Bridgeman MB. Ulipristal Acetate (ella): A Selective Progesterone Receptor Modulator For Emergency Contraception. P T. 2011 Jun;36(6):325-31. PMID: 21785549; PMCID: PMC3138379.

Medical Definitions:

  1. Levonorgestrel is a “progestin (a synthetic progestogen), which is a type of medication that produces effects similar to those of the natural female sex hormone progesterone (the major progestogen in the body involved in the menstrual cycle, pregnancy, and embryo development.) Progestogens are commonly used in hormonal birth control and menopausal hormone therapy. Progestogens are used alone or in combination with estrogens (any of a group of steroid hormones which promote the development and maintenance of female characteristics of the body). Such hormones can also be produced artificially for use in oral contraceptives (birth control) or to treat menopausal and menstrual disorders.” MedicineNet explains that, “Although levonorgestrel and similar emergency contraception pills contain a higher dose of levonorgestrel than birth control pills, they work in a similar way to prevent pregnancy by stopping ovulation (the release of an egg from the ovary), preventing fertilization of an egg (when the male sperm combines with the female egg to create an embryo with its own unique DNA), or preventing the attachment (implantation) of a fertilized egg to the uterus (womb).” According to DrugBank, “levonorgestrel works by binding to progesterone and androgen (a hormone that regulates the development and maintenance of male characteristics in vertebrates) receptors and slowing the release of gonadotropin-releasing hormone (GnRH – responsible for the release of follicle-stimulating hormone and luteinizing hormone from the anterior pituitary) from the hypothalamus, which links the nervous system to the endocrine system via the pituitary gland. This process results in the suppression of the normal physiological luteinizing hormone (LHLH – secreted by the anterior pituitary gland that stimulates ovulation in females) surge that precedes ovulation. It inhibits the rupture of follicles and viable egg release from the ovaries.”


  1. Ulipristal acetate is a “selective, reversible progestin receptor modulator, which is an agent that acts on the progesterone receptor, the biological target of progestogens like progesterone. Its tissue targets include the uterus, cervix, ovaries, and hypothalamus. Ulipristal acetate may act as an agonist (drugs that bind to and activate a given receptor but have only partial efficacy at the receptor) or antagonist (a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist) in the presence or absence of progesterone based on the tissue target.” According to DrugBank, “The pharmacodynamics of ulipristal acetate depends on the timing of administration in the menstrual cycle. If given mid-follicular phase, folliculogenesis (the maturation of the ovarian follicle, a densely packed shell of somatic cells that contains an immature oocyte, or egg before it matures) is delayed and estradiol (an estrogen steroid hormone and the major female sex hormone) concentrations decrease. If given at the time when the luteinizing hormone (LH – a hormone secreted by the anterior pituitary gland that stimulates ovulation in females) peaks, follicular rapture is delayed by several days. If given early-luteal phase, a decrease in endometrial (the inner lining or layer, along with its mucous membrane, of the uterus) thickness can be observed. The exact mechanism of action of ulipristal acetate has been heavily debated. On one hand, the majority of official prescribing information labels, monographs, and prior research studies for ulipristal indicated as an emergency contraceptive suggest that its primary mechanism of action revolves around inhibiting or delaying ovulation by suppressing surges in LH that result in the postponement of follicular rupture. Conversely, some of the latest investigations pertaining to ulipristal’s mechanism of action as an emergency contraceptive propose that it principally elicits its action by preventing embryo implantation, as opposed to preventing ovulation.”


  1. Mifepristone is also known as RU-86. According to DrugBank, it is a “synthetic steroid with effects of an antiprogestogen, a class of drugs which prevent progestogens like progesterone from mediating their biological effects in the body. They act by blocking the progesterone receptor and/or inhibiting or suppressing progestogen production. These effects are indicated for the medical termination of intrauterine pregnancy through 49 days’ pregnancy. Doses of 1 mg/kg or greater of mifepristone have been shown to antagonize the endometrial (lining of the uterus) and myometrial (the middle layer of the uterine wall) effects of progesterone in women. During pregnancy, the compound sensitizes the myometrium to the contraction-inducing activity of prostaglandins (any of a group of cyclic fatty acid compounds with varying hormonelike effects, notably the promotion of uterine contractions.) Mifepristone also exhibits antiglucocorticoid (a drug which reduces glucocorticoid – a corticosteroid that helps metabolize carbohydrates, proteins and fats and has anti-inflammatory activity in the body) and weak antiandrogenic (a class of drugs that prevent androgens like testosterone and dihydrotestosterone from mediating their biological effects in the body) activity. The anti-progestational activity of mifepristone results from competitive interaction with progesterone (the major progestogen in the body involved in the menstrual cycle, pregnancy, and embryo development) at progesterone-receptor sites. The termination of pregnancy results.”


  1. Misoprostol is, according to Obstetrics & Gynecology, “a synthetic prostaglandin (any of a group of cyclic fatty acid compounds with varying hormonelike effects, notably the promotion of uterine contractions) E1analog used to reduce the risk of NSAID (nonsteroidal anti-inflammatory drugs used to reduce pain, decrease fever, prevent blood clots, and in higher doses, decrease inflammation) related ulcers. The stimulation of prostaglandin receptors in the stomach reduces gastric acid secretion. However, stimulating these receptors in the uterus and cervix can increase the strength and frequency of contractions and decrease cervical tone. Misoprostol is used off-label for a variety of indications in the practice of obstetrics and gynecology, including medication abortion, medical management of miscarriage, induction of labor, cervical ripening before surgical procedures, and the treatment of postpartum hemorrhage.”


  1. Embryo – the developing human individual from the time of implantation in the uterus to the end of the eighth week after conception, at which point the embryo is termed a fetus; the laying down of fundamental tissues, and the formation of primitive organs and organ systems.


  1. Body Mass Index (BMI) – a measure of body fat based on height and weight that applies to adult men and women. You can calculate your BMI here.


  1. Barbiturates are used as sedatives (to produce a calming effect), as hypnotics (to produce sleep), or to aid anesthesia, according to Brittanica. “Barbiturates are derivatives of barbituric acid (malonyl urea), which is formed from malonic acid and urea. Barbiturates act by depressing the central nervous system, particularly on certain portions of the brain, though they tend to depress the functioning of all the body’s tissues. Most of them exert a sedative effect in small doses and a hypnotic effect in larger doses. Barbiturates are classified according to their duration of action. The effects of long-acting barbiturates, such as barbital and phenobarbital, may last for as long as 24 hours; these drugs are used in conjunction with other drugs for the treatment of epilepsy, in which their prolonged depressant action helps prevent convulsions. Barbiturates of intermediate duration of action, such as amobarbital and butabarbital sodium, act for 6 to 12 hours and are used to relieve insomnia. Short-acting barbiturates, such as pentobarbital and secobarbital, are used to overcome difficulty in falling asleep. Ultrashort-acting barbiturates, such as thiopental sodium and thiamylal, are used intravenously to induce unconsciousness smoothly and rapidly in patients about to undergo surgery, after which gaseous anesthetics are used to maintain the unconscious state. The prolonged use of barbiturates—especially secobarbital and pentobarbital—may cause the development of a tolerance to them and require amounts much larger than the original therapeutic dose. Denial of a barbiturate to the habitual user may precipitate a withdrawal syndrome that is indicative of physiological dependence on the drug. An overdose of barbiturates can result in coma and even death due to severe depression of the central nervous and respiratory systems.”


  1. Ectopic Pregnancy. MedicineNet defines an ectopic pregnancy as a pregnancy(the time during which one or more offspring develops inside a woman) that is not in the uterus (womb). “The fertilized egg settles and grows in any location other than the inner lining of the uterus. The large majority (95%) of ectopic pregnancies occur in the Fallopian tube (either of a pair of tubes along which eggs travel from the ovaries to the uterus in a female). However, they can occur in other locations, such as the ovary (an organ found in the female reproductive system that produces an ovum/egg). When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm); cervix (the lowest region of the uterus that attaches the uterus to the vagina (the elastic, muscular part of the female genital tract that extends from the vulva to the cervix and provides a passage between the vaginal cavity and the uterine cavity); and abdominal cavity (a large body cavity in humans and many other animals that contains many organs). An ectopic pregnancy occurs in about 1 in 60 pregnancies. Most ectopic pregnancies occur in women 35 to 44 years of age. Ectopic pregnancies are frequently due to an inability of the fertilized egg to make its way through a Fallopian tube into the uterus. Sharp, stabbing pain is usually the first symptom of an ectopic pregnancy. Diagnosis of an ectopic pregnancy includes a pelvic exam to test for pain, tenderness or a mass in the abdomen; the measurement of the hormone hCG (human chorionic gonadotropin; ultrasound (an imaging test that uses sound waves to create a picture, or sonogram, of organs, tissues, and other structures inside the body); or sometimes culdocentesis, the insertion of a needle through the vagina into the space behind the uterus to see if there is blood there from a ruptured Fallopian tube. Treatment of an ectopic pregnancy is surgery. A ruptured tube usually has to be removed. If the tube has yet not burst, it may be possible to repair it.”



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