The morning-after pill following unprotected sex

These medications are usually effective in preventing pregnancy for up to five days after an episode of unprotected sex but work best if used as soon as possible after the event.

These medications interfere with the hormone pattern necessary for a pregnancy to occur by preventing an egg from implanting in the uterus or can prevent ovulation from occurring. Even women who should not take estrogen-containing birth control pills can take these medications if needed.

What are they and how do I get them?

There are three forms of emergency contraceptive pills. 

The first option is progestin-only pills. These are available over the counter. You will need to ask the pharmacist for them but you do not need a prescription if you are 17 or older. Brand names are Plan B One-step, Next Choice, and Take Action. Take these pills as directed as soon as possible after sex and not more than five days afterward. This method is less effective in those who weigh more than 165 pounds.

The second option is combined estrogen/progesterone pills. You should contact a physician or contraceptive clinic to get the pills in the correct dosage, which varies from brand to brand. Depending on the type of pill used, you need to take two to four pills as soon as possible after unprotected sex and then another two to four pills 12 hours later. Once again you want to take these as soon as possible after the event and not more than five days later. This method is less effective than the other two methods and has more side effects.

The third option is an antiprogestin pill called Ella. It requires a prescription and once again can be taken up to five days after sex. You cannot take any type of hormonal contraceptive for five days following this medication. This method is more effective in heavier women than the other two pill options.

What are the side effects?

While highly effective in preventing pregnancy, these treatments are not a substitute for regular forms of contraception nor are they without side effects.

The progestin only method is less likely to cause nausea (18 percent) and vomiting (4 percent).

With the combined estrogen/progesterone pills, 43 percent of women may experience nausea from the high estrogen levels and 16 percent may experience some vomiting. A small number may experience breast tenderness or headache.

All these methods may cause a change in your bleeding pattern. Ella will cause a delay in your period. Others may cause spotting.

I’ve taken the medication. Now what?

You must use a birth control method for the remainder of your cycle. If you don’t, you will need to retake the emergency contraceptive. You can restart your birth control pill, ring, or patch the following day unless you took Ella. You will need to use condoms or abstain from sex for the next seven days until your birth control is effective again.

If you do not have a period by three weeks after taking the medication or you have continued irregular bleeding, you should perform a pregnancy test.

Whatever your form of birth control, remember that only condoms protect against both pregnancy and sexually transmitted disease. A condom is essential unless you are in a monogamous relationship and know that you and your partner are free of sexually transmitted infections.

Are there any other options?

Paragard IUDs can be placed within five days of unprotected sex for prevention of pregnancy. This is a very effective form of emergency contraception with only 1 out of 1,000 women becoming pregnant afterward. This is the most effective emergency contraception available for heavier women. The IUD can be left in place for 10 years. There are risks with placement, including pain, infection, perforation of the uterus, and expulsion of the IUD at a later date. Periods can be heavier and crampier with this type of IUD. Same day placement may not be available at all clinics.