Emergency contraception 

This refers to birth control taken to prevent pregnancy after an unprotected or inadequately protected act of intercourse. It is sometimes called "the morning after pill", even though it consists of more than one pill. At the present time the FDA approves two medications for this use: one with progestin (levonorgestrel) only pills and another with combination estrogen progestin oral contraceptive. Of the two, the levonorgestrel method (brand name Plan B) is the more effective and has fewer side effects. This method is believed to prevent at least 74% of unwanted pregnancies. (2) 

It is interesting to note that emergency contraception is a source of political debate. Previously, it was believed to act by impairing implantation and also by inhibiting ovulation. Thus, as a medication which prevented implantation it was viewed as an abortificant, or a medication which causes abortion. Based on this it was controversial and underused. However, 2010 data recently brought to light has disproven this theory, at least in the case of the levonorgestrel containing preparations such as "Plan B".  (3) FIGO, the International Federation of Obstetricians and Gynecologists has issued a statement unequivocally confirming that Plan B does not cause abortions. (4)  Accurate media discussion of this data may make the method acceptable to a larger group of women.

Media discussion of this method may make more people aware of it. Numerous studies have shown that reproductive age women and their caregivers alike are unaware of this method or are not in the habit of discussing it. (2) Emergency birth control is safe for women even if they have contraindications to regular oral contraceptives. Therefore emergency birth control has been made available to women 17 years of age or older, over the counter, without a prescription. 

Need nighttime photo of Walgreens here with bold caption

For emergency contraception to be effective, it should be taken within five days of unprotected intercourse. The sooner it is taken the more effective it is. Although vomiting with the levonorgestrel preparation is rare, it is not unheard of. Therefore if vomiting occurs within two hours of taking the dose, it should be repeated and may be administered vaginally. Since the morning after pill simply delays ovulation, the patient still may be fertile in the later part of the cycle. She should therefore begin a short-term form of contraception with the assistance of her caregiver. Longer-term forms of contraception are also available, once it is established that a pregnancy has not occurred. If the patient's period in that cycle is delayed more than a week, she should take a pregnancy test and seek evaluation with her caregiver.

THE MORNING AFTER PILL " PLAN B" DOES NOT CAUSE ABORTION. 

2.Emergency contraception. Practice Bulletin No. 112. AMerican College of Obstetricians and Gynecologists. Obstet Gynecol 2010;115;1100-9

3. Contraception. 2010 May;81(5):414-20. doi: 10.1016/j.contraception.2009.12.015. Epub 2010 Jan 27. 

4. figo.org