In the last few weeks, emergency contraception (EC) has gotten a lot of attention as the courts, the Food and Drug Administration (FDA), and the Obama administration worked out their differences (or put them aside) and agreed that one version of EC, Plan B One-Step, would be made available over-the-counter to women of all ages. This is a big step forward in efforts to expand access to contraception and, in turn, to prevent unintended pregnancies. Still, we have to remember that emergency contraception is not meant to be anyone’s primary method of birth control—it is taken after an act of sexual intercourse in which the couple forgot to use another method or used a method incorrectly, or in which the method failed. Here’s a quick review of methods that can be used effectively to prevent pregnancy.

Hormonal Methods

The birth control pill revolutionized contraception (and perhaps sexual relations) when it was introduced in the 1960s. Birth control pills were the first kinds of hormonal contraception. They work primarily by preventing ovulation (if there is no egg, there can be no fertilization and no pregnancy). Birth control pills and subsequent hormonal methods also thicken cervical mucus in order to prevent sperm from getting into the uterus.

Today, young women have numerous hormonal methods to choose from. The pill remains hugely popular, and there are many different kinds available; some run on a 21/7 cycle (meaning women take hormones for 21 days and then break for seven, during which time they get their period), others 24/4, and still others limit menstruation to just four times a year.

For women who don’t want to swallow a pill every day or think they’ll have trouble remembering to do it, there are other hormonal methods that do not require daily action. The contraceptive patch, for example, which is sold under the brand name Ortho-Evra, is a bandage-like sticker that a woman wears on her upper arm, buttocks, back, or abdomen. It releases hormones through the skin. Women using the patch change it every week for three weeks. During the fourth week, they wear no patch and then get their periods.

Women can also choose the contraceptive ring. Sold as NuvaRing, this is a flexible piece of plastic that looks a little like a bracelet and is inserted into the vagina (the exact position isn’t important). It is left in for three weeks while it releases hormones. The user can then remove it, get their period, and put in a new one a week later. If inserted properly to begin with, most users don’t even feel it.

One of the older and more well-known hormonal methods is Depro-Provera, sometimes called the contraceptive shot. Women get an injection from their health-care provider every three months and are protected from pregnancy during that time.

If used perfectly, hormonal methods are all over 99 percent effective. People do make mistakes, however: they may forget to take a pill, forget to pick up a prescription for the patch, or forget to make an appointment to get a shot in time. For these reasons, the typical use failure rates are a little higher—they are between 91 and 94 percent effective. This means that out of every 100 couples who use hormonal methods, six to nine will experience an unintended pregnancy during their first year of use. Continuing users have lower rates of contraceptive failure than first-year users, as they become more accustomed to use.

Long-Acting Reversible Contraception (LARC) Methods

Contraceptive implants, which are now sold under the brand names Implanon and Nexplanon, are also hormonal methods, but last much longer. A single rod—about the size of a matchstick—is implanted by a health-care professional under the skin on the inside of a woman’s upper arm. It steadily releases hormones into a woman’s body for three years. These long-acting reversible contraception (LARC) methods last a long time but can be removed at any time and fertility will return quickly.

Implants were developed in the early 1980s and first approved by the FDA in 1990 under the brand name Norplant, which worked well but was taken off the market in 2002. At the time, the manufacturer cited “limitations on component supplies,” but difficulties with the removal process and negative public opinion were also clearly a factor in the decision. 

The new generation of implants was approved by the FDA in 2006. These single-rod implants are much easier for health-care providers to insert and remove. 

Intrauterine devices (IUDs), which are also considered to be LARCs, are flexible plastic devices that are inserted into the uterus to prevent pregnancy. IUDs prevent pregnancy by interfering with the movement of sperm toward eggs, thereby inhibiting fertilization. They may also change the lining of the uterus, preventing implantation of a fertilized egg (though this theory has not been proven) and thicken cervical mucus.

There are currently three IUDs on the market in the United States. ParaGard (also known as the Copper-T) releases a small amount of copper into the uterus and lasts ten years. Mirena releases a hormone similar to that in some birth control pills, which means it may also prevent ovulation in some women; it lasts for five years. The newest introduction to the market is called Skyla. It is also a hormonal IUD; it has been designed to be smaller and is specifically meant for younger women. Skyla lasts for three years. 

IUDs have a bit of a sordid history in the United States. They were first introduced in the 1960s and became quite popular. In fact, by the next decade there were over 17 models in development by 15 different companies. One model, the Dalkon Shield, had serious design flaws which resulted in higher rates of pelvic inflammatory disease (PID) in users, causing scarring in the uterus and fallopian tubes and, for many of these women, increased infertility. The Dalkon Shield also had a higher failure rate than expected, and women who became pregnant while using it risked spontaneous septic abortions (miscarriages followed by infection). Eighteen deaths were attributed to the Dalkon Shield, and more than 400,000 lawsuits were brought against the manufacturer. Though the design flaws were unique to the Dalkon Shield, public opinion of all IUDs soured, and by 1986 there was only one model of IUD on the market in the United States, and few women were using it.

ParaGard and Mirena became available in the early 2000s, but the FDA initially only approved them for use in women who had already had children. Research has shown, however, that they are safe for women of all ages, regardless of whether they’ve had children. Last summer, the American College of Obstetrics and Gynecology recommended that IUDs be among the first line of contraceptives offered to adolescents.

LARC methods are highly effective in part because user error is essentially taken out of the equation. The “get it and forget it” aspect of these methods means that perfect use and typical use rates are the same—IUDs are more than 99 percent effective.

For this reason, some in the public health world have started to see LARCs as the magic bullet for teen pregnancy—put one in at 15 and without changing her behavior or managing any medicines a girl can make it out of her teen years pregnancy-free. Though there has been an increase in the number of teens using both IUDs and implants over the past few years, these methods are not yet extremely popular with teens. Between 2008 and 2010, for example, only 4.4 percent of teens who were using contraception were using an IUD.

Don’t Forget the Condom

Condoms may be the original “plan B” for many teenagers, because unlike all the other methods they require almost no forethought. For those teens who find themselves hot and heavy but are not on the pill and don’t have an IUD, there is always the condom. Even if she doesn’t already have one in her purse and he doesn’t have one in his wallet, a teen is never far from a condom because this inexpensive form of birth control, which works by going over the penis and preventing sperm from entering the vagina, can often be purchased at a drug store, convenience store, or even a gas station.

If used perfectly, condoms are 98 percent effective, which is similar to hormonal methods. Typical failure rates are higher than those of other methods (about 18 of 100 couples using condoms as their primary method will experience a pregnancy in the first year of use) because people make mistakes—like putting it on too late, taking it off too soon, or opening the package with something sharp. Typical use rates for condoms also include those couples who say condoms are their primary method of contraception but weren’t actually using a condom when they got pregnant.

Using a condom correctly is not difficult, so instead of waiting until the next day to go to the drug store for emergency contraception, couples can hit the RiteAid or CVS for condoms before sex (even if it means taking a quick break from all the kissing and groping).

In fact, even those people who are on other birth control methods should consider hitting the condom aisle before a big date because—other than not having sex—condoms are the only way to prevent sexually transmitted infections (STIs). None of the other methods we talked about here prevent STIs.    

The ideal situation, of course, is dual use, where couples who want to avoid pregnancy use LARC methods for birth control and continue to rely on condoms to prevent STIs, including HIV. The good news is that more young couples are doing so; according to a recent National Survey of Family Growth 23 percent of teens reported dual use between 2008 and 2010 (up from 16 percent between 2006 and 2008).

Expanded access to emergency contraception is critical and represents a huge step forward in preventing unintended pregnancies. Still, we have to remember that, in the ideal world, emergency contraception would hardly ever be needed, because everyone would have the information and access they needed to use other reliable methods correctly and would be able to protect themselves against pregnancy and STIs in the moment every time they had sex.