Reasons for Use
Emergency contraception is indicated following incidents where the risk of unintended pregnancy exists. The primary cause for its use is unprotected sexual intercourse, which may occur due to a lack of contraceptive use, sexual assault, or the failure of a primary birth control method. Common examples of contraceptive failure include a condom breaking or slipping, missing multiple doses of oral contraceptive pills, being late for a contraceptive injection, or miscalculating fertile days during natural family planning.

Biological Mechanisms
The medication or device works by interrupting the biological processes required for pregnancy. Levonorgestrel and ulipristal acetate pills primarily function by delaying or inhibiting ovulation, meaning they stop the ovary from releasing an egg while sperm are present. Copper intrauterine devices (IUDs) work by creating an environment that is toxic to sperm and eggs, preventing fertilization or implantation. These methods do not end an established pregnancy where implantation has already occurred.

Factors Influencing Effectiveness
Certain factors can reduce the efficacy of emergency contraception. The most critical risk factor for failure is the timing of administration; effectiveness decreases significantly the longer a person waits after unprotected sex. Additionally, body mass index (BMI) may influence outcomes; some studies suggest that levonorgestrel pills may be less effective in individuals with a higher BMI, whereas the copper IUD retains high efficacy regardless of weight. Interactions with certain medications, such as enzyme-inducing drugs used for epilepsy or tuberculosis, can also lower effectiveness.

Prevention Strategy
Emergency contraception is a form of secondary prevention—a backup method rather than a primary strategy. Primary prevention of unintended pregnancy involves the consistent and correct use of routine contraceptives, such as condoms, birth control pills, patches, rings, implants, or IUDs. Relying solely on emergency methods is not recommended due to lower efficacy compared to regular methods and the potential for cycle disruption.

Clinical Assessment
Unlike a disease that is diagnosed, emergency contraception is an intervention administered based on a patient's history. Clinicians identify the need for it by discussing the timing of the last menstrual period to estimate the risk of ovulation and confirming the time elapsed since unprotected intercourse. Before administering certain types, such as the IUD or ulipristal acetate, a healthcare provider may perform a pregnancy test to ensure an established pregnancy does not already exist, as emergency contraception is ineffective for existing pregnancies.

Physical Side Effects
While the intake of emergency contraception does not have "symptoms," the medication often causes acute physical side effects that mimic early pregnancy or premenstrual syndrome. Users frequently report nausea, which is one of the most common reactions, sometimes accompanied by vomiting. Other systemic effects include fatigue, dizziness, and headaches. In the reproductive system, women may experience lower abdominal pain, pelvic cramping, and breast tenderness. These physical effects are typically mild and resolve without treatment.

Menstrual Changes
A significant sign of the medication's effect is a change in menstrual bleeding patterns. Users may experience spotting or irregular bleeding shortly after taking the pill. The next menstrual period may arrive earlier or later than expected and may be heavier or lighter than usual. If a period is more than a week late, clinicians generally recommend a pregnancy test to rule out failure of the method.

Medication Options
The most common treatment involves oral medications known as "morning-after pills." Levonorgestrel pills are available over-the-counter and are most effective when taken within 72 hours of unprotected sex. Ulipristal acetate is a prescription-only medication that is effective for up to 120 hours (5 days) and may work closer to the time of ovulation than levonorgestrel. These medications are single-dose or two-dose regimens designed to act quickly.

Intrauterine Devices (IUDs)
The most effective form of emergency contraception is the insertion of a copper IUD by a healthcare professional within 5 days of unprotected sex. Some hormonal IUDs are also approved for this use. This method serves a dual purpose: it acts as emergency contraception and provides highly effective, long-term birth control for years depending on the device chosen.

Lifestyle and Self-Care
Managing side effects typically involves rest and home remedies. Taking the medication with food can help reduce nausea. If vomiting occurs within two hours of taking an oral dose, a replacement dose is usually required, and a doctor should be contacted immediately. Over-the-counter pain relievers can manage headaches or cramps. It is also important to abstain from sex or use a barrier method (like condoms) until the next menstrual period, as the pill does not protect against future acts of unprotected sex.

When to See a Doctor
Medical attention is rarely needed for the administration of over-the-counter pills, but follow-up is necessary in specific situations. Seek medical care if you experience severe, persistent lower abdominal pain, as this could indicate an ectopic pregnancy, a rare but serious complication. A doctor should also be consulted if your period does not start within three to four weeks after treatment, if bleeding is unusually heavy, or if you suspect you might be pregnant. Routine follow-up is generally not required unless initiating a new form of regular birth control.

Efficacy and Reliability
Emergency contraception is not 100% effective, but it significantly lowers the risk of pregnancy. The copper IUD is more than 99% effective. Oral pills reduce the risk by 75% to 89%, depending on the type and how quickly they are taken. The "severity" of the situation relies heavily on timing; the sooner the method is used, the better the outcome. It is less effective than consistent use of standard hormonal birth control methods.

Duration of Side Effects
The physical effects of emergency contraception are acute and short-lived. Symptoms like nausea, headache, and fatigue typically resolve within 24 to 48 hours. Menstrual disturbances, such as spotting or a delayed cycle, are temporary and usually normalize by the following menstrual cycle. There are no chronic forms of illness associated with the correct use of these medications.

Long-Term Outlook and Complications
There are no known long-term negative health effects or risks to future fertility from using emergency contraception, even if used more than once. It does not cause birth defects if the method fails and pregnancy occurs. The primary complication is method failure resulting in unintended pregnancy. In rare cases, if pregnancy occurs despite treatment, there is a need to rule out ectopic pregnancy (pregnancy outside the uterus), although the medication itself does not cause this condition.

Work and Daily Activities
Most people can continue with work, school, and normal daily activities immediately after using emergency contraception. However, side effects like nausea or fatigue may temporarily reduce energy levels. It is advisable to have a quiet day or access to a restroom if nausea is severe. If an IUD is inserted, some cramping may persist for a few days, potentially requiring brief rest or lighter physical activity.

Mental and Emotional Health
The need for emergency contraception can be accompanied by stress, anxiety, or fear regarding potential pregnancy or the circumstances of the sexual encounter. Waiting for the next menstrual period to confirm effectiveness can be an emotionally taxing period. Accessing support from a partner, friend, or counselor can be helpful during this waiting window.

Questions to Ask Your Healthcare Provider

• Which type of emergency contraception is most effective for my body weight and the time passed since unprotected sex?
• If I vomit after taking the pill, do I need another dose?
• How will this medication affect my current birth control cycle?
• When should I start regular birth control after taking this pill?
• What specific symptoms should prompt me to call you immediately?
• Can I get an IUD inserted for emergency contraception, and how soon can you do it?

Q: Is emergency contraception the same as the abortion pill?
A: No. Emergency contraception works by preventing pregnancy from starting (stopping ovulation or fertilization). The abortion pill (medication abortion) ends an established pregnancy. Emergency contraception will not work if you are already pregnant.

Q: Can I use emergency contraception as my regular birth control?
A: It is not recommended for regular use because it is less effective than standard birth control methods (like the pill, patch, or IUD) and can cause irregular periods and more frequent side effects. It is designed only for emergencies.

Q: Does emergency contraception affect future fertility?
A: No. There is no evidence that using emergency contraception, even multiple times, causes infertility or makes it harder to get pregnant in the future.

Q: Do I need a prescription to get emergency contraception?
A: Levonorgestrel pills (like Plan B) are available over-the-counter without a prescription or age restriction. Ulipristal acetate (Ella) requires a prescription. Copper IUDs must be inserted by a healthcare provider.

Q: How do I know if it worked?
A: The only way to know for sure is when your next period arrives. If your period is more than a week late, or if it is unusually light, you should take a pregnancy test.