Effectiveness of Emergency Contraception - FAQ's


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Effectiveness of Emergency Contraception

How effective is emergency contraception?
What is the most effective form of emergency contraception?
Is the Day After birth control as effective as emergency contraception?
What are Plan B effects that can occur after taking them for emergency contraception?
Are emergency contraceptive pills effective after 72 hours?
Can emergency contraceptive pills be used more than once in the same cycle?
How soon is the IUD effective after insertion into the uterus in preventing pregnancy?
Is emergency contraception less effective when enzyme inducers such as St. John’s Wort, Dilantin, antibiotics such as rifampin, or griseofulvin are being consumed?
What contraindications are there to taking emergency contraceptive pills?
What contraindications prevent the use of The Intrauterine Device (IUD) for emergency contraception?
How does plan b effectiveness compare with combined birth control pill or the Intrauterine Device (IUD) for emergency contraception?

How effective is emergency contraception?

More Frequently Asked Questions

Emergency contraception (morning after pills, day after pills, post coital contraception, day after contraception Plan B) can reduce the incidence of an unwanted pregnancy if used within 5 days of unprotected intercourse. The earlier after unprotected sex the Emergency Contraception is use, the higher the success rate in preventing pregnancy. Delaying taking Emergency Contraceptive pills until the second twelve hours after unprotected intercourse increases the risk of pregnancy form .9% to 1.8%. The type of Emergency Contraception used also is important in determining how successful the reduction in unwanted pregnancy will be as levonorgestrel (Plan B, Next Choice) is more effective in preventing pregnancy than combined oral contraceptive pills if taken 72 hours or less after unprotected intercourse (89% vs. 75%). The Intrauterine Device is over 99% effective in preventing a unwanted pregnancy if it is inserted in less than 120 hours (5 days) after unprotected intercourse (women don’t use birth control, their regular contraceptive fails, or they are raped.

If 100 women have unprotected sex one time during the second or third week of their monthly menstrual cycle, it is expected that 8 of them will become pregnant. If those same 100 women use combined oral contraceptive pills for emergency contraception 2 pregnancies will occur. If Plan B or Next Choice is used, one will become pregnant. If the IUD is inserted, then less than .5 of those women become pregnant.

Both types of emergency contraceptive pills and the IUD are safe and effective methods used in preventing unwanted pregnancies. Emergency Contraceptive pills used as the primary method of birth control have a very high incidence of pregnancy occurring within a year of usage. 40% of patients who use combined progestin and estrogen pills and 20% who use progestin only (levonorgestrel, Plan B or Next Choice) become pregnant. Demographic and health surveys show that 1-2 out of hundred become pregnant with ongoing usage with the IUD, 6 out of 100 with use of birth control pills, 12 out of hundred with withdrawal, 18 out of hundred with condoms, 19.9 out of hundred with the rhythm method.

As can be seen, Emergency Contraception is not to be relied upon as a primary form of birth control. Condom usage, withdrawal method, and the rhythm method are more effective over a one year period of time than Emergency Contraceptive pills at preventing pregnancy. All Physicians and medical personnel involved with family planning should recommend that all women of reproductive age should be on a regular method of contraception to prevent unintended pregnancies.

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What is the most effective form of Emergency Contraception?

The most effective form of Emergency Contraception is the Intrauterine Device (IUD). If inserted in less than 5 days after unprotected intercourse it reduces the incidence of an unwanted pregnancy by over 99 percent. It can be inserted beyond 5 days of unprotected intercourse as long as it does not occur beyond 5 days after ovulation as the IUD will have no effect in preventing implantation or post implantation (abortion) All women should be offered the IUD as the number one choice for Emergency Contraception especially if the woman needs a long term contraceptive method. Ideally, an emergency IUD should be inserted immediately at the first presentation if she is a candidate. If she is not a candidate and there must be a delay in insertion, then Plan B (Next Choice, levonorgestrel) should be offered.

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Is the Day After Birth Control As Effective As Emergency Contraception?

Day After (morning after pill, post coital contraception, day after contraception, Plan B) are words that have the same meaning and used interchangeably and synonymous with Emergency Contraception. The word Day After or Morning After Pill can be rather confusing since Emergency Contraceptive can be and should be used immediately after unprotected intercourse. This is due to the Day After Pill (Emergency Contraceptive Pill, morning after pill) being more effective immediately after the unprotected sex episode. There is a 95% reduction in pregnancy when women take the Day After Pill within the first 24 hours of unprotected sex. The pregnancy rate doubles if the Day After Pill is taken in the second 12 hours of unprotected sex rather than the first 12 hours after unprotected intercourse (0-12 hours .9% incidence of pregnancy; 13 to 24 hours-1.8% incidence of pregnancy). The incidence of pregnancy increases to 4.3 percent between 60 to72 hours after unprotected intercourse after taking Emergency Contraceptive Pills. (Day After). The Day after pill was found to be effective up to 120 hours or 5 days after unprotected intercourse where between 73 and 120 hours the incidence of pregnancy was decreased by 64%. There are no studies to determine if the Day After Pill is effective after 120 hours.

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What are Plan B effects that can occur after taking them for Emergency Contraception?

Plan B is composed of a progestin-only (levonorgestrel) tablet. It is safe and well tolerated as an Emergency Contraceptive. 14% of patients experience nausea and 1 % experience vomiting. On the other hand, patients who take combined birth control pills for Emergency Contraception, 50% of patients experience nausea, and 20 % have vomiting.

Plan B is safe and well tolerated. Side effects do occur but they are less frequent than what occurs with taking combined oral contraceptive pills (birth control pills) that are used for Emergency Contraception (morning after pill, day after pill, post coital contraception, day after contraception). The most common side effects include headaches, nausea, vomiting, dizziness, headache, fatigue, breast tenderness, lower back pain, lower abdominal pain, ankle swelling, and abnormality of their menses. The menses could be heavier, lighter, start earlier or later than normal. More than 95% of patients start their menses at the expected time or within 7 days of when their menses is supposed to start. Patients should be told that if their period is more than a week late, they possibly could be pregnant. If a patient develops severe abdominal or pelvic pain, ectopic pregnancy should be expected and she should be evaluated by medical personnel.

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Are Emergency Contraceptive Pills effective after 72 hours?

Emergency Contraceptive Pills (morning after pill, day after pill, post coital contraception, day after contraception, Plan B) have been studied for years and found to be highly effective when taken 72 hours or less after unprotected intercourse. Plan B (Next Choice or levonorgestrel) are 89% and combined estrogen and progestin oral contraceptive pills are 75% effective in preventing unwanted pregnancy when taken in less than 72 hours. Emergency Contraceptive pills are more effective the sooner they are taken after the incident of unprotected sex. If taken in less than 12 hours, there is only a .9% chance of becoming pregnant whereas is taken at the 60 to 72 hour point, there is a 4.3% chance of becoming pregnant. When taken between 72 and 120 hours, there is 63% chance of expected pregnancies that are prevented versus 89% when taken less than 72 hours after unprotected intercourse. No data have been identified relating the use of levonorgestrel for Emergency Contraception beyond 120 hours.

The IUD can be used up to 120 hours (5 days) after unprotected intercourse and reduce the incidence of pregnancy up to 99%. Thus for women who present after 72 hours, the IUD should be offered as the number one method of preventing an unwanted pregnancy.

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Can Emergency Contraceptive Pills be used more than once in the same cycle?

Yes. Emergency Contraceptive Pills (morning after pill, day after pill, post coital contraception, day after contraception, Plan B) can be used more than once in a cycle. Giving repeat doses of the Emergency Contraceptive pill prior to the LH surge may be effective and further unprotected sex may be an indication for repeat Emergency Contraceptive usage. Repeated dosages will not induce abortions in women who are already pregnant. No additional Emergency Contraceptive pills are required if unprotected intercourse occurs within 12 hours of a dose of Emergency Contraception.

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How soon is the IUD effective after insertion into the uterus in preventing pregnancy?

The IUD is considered to become effective immediately after insertion by causing a local inflammatory reaction that is more pronounced in the presence of copper. It primarily impairs ova viability (ovaricidal) before fertilization occurs.

The risk of pregnancy varies throughout the menstrual cycle, increasing around the time of ovulation (day 10-17) to 30%. It is accepted that there is very little risk of ovulation to occur up to day 7 of the menstrual cycle but it is theoretically possible that ovulation can occur any time during a menstrual cycle though unlikely for women who have regular menstrual cycles.

There are less than 20 in 1000 women who become pregnant over 5 years with a IUD in place, The option of an IUD with its low failure rate as an Emergency Contraceptive and the potential for use as an ongoing method of contraception should be discussed with all women requesting Emergency Contraception even if they present within 72 hours of unprotected sex.

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Is Emergency Contraception less effective when enzyme inducers such as St. John’s Wort, Dilantin, antibiotics such as rifampin or griseofulvin, or are being consumed?

There are certain medications and herbal supplements that can increase cytochrome p450 in the liver that is able to increase the metabolism of certain drugs and reduce or inhibit their effectiveness altogether. One of the medications that lose their effectiveness are birth control pills and emergency contraceptive pills by increasing the metabolism of ethinylestradiol and progestins. So if enzyme inducing drugs are being used such as St. John’s Wort, Dilantin, bexarotene, carbamazepine, ethotoin, felbamate, oxcarbazepine, topiramate, modafinil, pioglitazone, rifabutin, rifapentine, some medicines to treat HIV infection like atazanavir, indinavir, lopinavir, nelfinavir, tipranavir, ritonavir, the antibiotics rifampin or griseofulvin should be advised to take a total of 3mg (2 tablets) of as a single dose of Plan B or Next Choice as soon as possible and within 72 hours. This is outside the product license and there are no studies have been found to confirm that this increase in dose is actually required. If using birth control pills for Emergency Contraception the first set of pills taken should be doubled. By increasing the dosage there is a higher incidence of nausea and vomiting. To possibly decrease the chance of this occurring, 2 twenty-five milligrams of meclizine (for nausea) can be taken one hour before taking the oral contraceptives for Emergency Contraception.

Women using liver enzyme-inducing drugs should be advised that an IUD is the preferred option for Emergency Contraception. There are no drugs that are known to affect emergency IUD use.

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What contraindications are there to taking emergency contraceptive pills?

There are no medical contraindications to the use of Emergency Contraceptive pills (morning after pill, day after pill, post coital contraception, day after contraception, Plan B). Women with hepatic abnormalities, galactose intolerance, lactose deficiency, glucose-galactose malabsorption, and Crohn’s disease may all experience a reduction in efficacy with the use of Emergency Contraceptive pills.
Effectiveness of Emergency Contraception

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What Contraindications Prevent the Use of The Intrauterine Device (IUD) for Emergency Contraception?

Use of an IUD for Emergency Contraception carries the same contraindications as routine IUD insertion:

WHO Category 4: Conditions that rule out use of copper-bearing IUDs

  1. Pregnancy
  2. Active STD (purulent Cervicitis) or PID now or in last 3 months.
  3. Sepsis following childbirth or abortion
  4. Undiagnosed vaginal bleeding
  5. Severely distorted cavity that prevents proper IUD insertion
  6. Cervical, endometrial or ovarian cancer awaiting treatment, malignant trophoblastic disease
  7. Pelvic Tuberculosis

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How does Plan B effectiveness compare with combined birth control pill or the Intrauterine Device (IUD) for Emergency Contraception?

Plan B effectiveness is more effective than combined birth control and less effective than the IUD. The sooner birth control pills are taken after unprotected sex, the less chance of becoming pregnant. Plan B decreases the incidence of pregnancy if taken within the first 24 hours by 95%. If Plan B is taken in less than 72 hours of unprotected intercourse, the incidence of pregnancy is reduced by 89%. For combined oral contraceptives if taken 72 hours or less, the incidence of pregnancy is reduced by 75%.

The IUD is over 99% effective in reducing the incidence of pregnancy if inserted 120 hours (5 days) or less after unprotected intercourse. There are very few side effects with the IUD if patients are properly screened and there are no contraindications to its use.

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