It was the early 1960's and tent dresses, white go-go boots, and Vidal Sassoon haircuts were all the rage.

But what captured the attention of most women was the "pill" -- a new method of pregnancy protection that promised to revolutionize a woman's sex life. And it did.

Today there are more than 40 different configurations of the pill available -- along with more than a half dozen other methods to easily prevent pregnancy.

"It is safe to say that we can offer women a lot more options than in the past, including not only the ability to control when and how often she wants to get pregnant, but also many aspects of the reproductive cycle, including bleeding patterns, menstrual pain, and even PMS," says Randy A. Fink, MD, a gynecologist in Miami who has advised the FDA on many of the latest contraception entries.

Indeed, in recent months, we've seen a number of advances in pregnancy protection take center stage. Here's a look at some of the newest options -- and how they can work for you.

Not Your Mother's Birth Control

Method: Plan B

If you need birth control and you need it fast -- after unprotected sex has occurred -- then you need Plan B, a method of contraception recently approved by the FDA for over-the-counter use in women age 18 and older. As the name implies, its main purpose is for emergency contraception: after the condom breaks, you forget to take the pill, or sex happens unexpectedly.

How It Works: Plan B primarily prevents pregnancy by stopping the release of an egg from an ovary, and may also prevent the fertilization of an egg by sperm. According to Rachel Masch, MD, it works by "thickening cervical mucous to block sperm from meeting the egg, plus it thins the uterine lining so implantation can't occur."

Plan B has been controversial because of the way it interferes with pregnancy. Masch, director of family planning at Bellevue/NYU Medical Center, says Plan B "does not cause an abortion -- it prevents pregnancy."

Some anti-abortion advocates do not agree with Masch's assessment and have opposed the legalization and use of Plan B.

What You Should Know: Available without a prescription, Plan B is safe to take as directed, even if you are currently using other hormonal methods of birth control or hormone replacement therapy. That said, doctors warn women not to use Plan B as their regular form of birth control.

"It's called Plan B for a reason -- there should be a 'plan A' in place if you are having sex," says Masch. Side Effects: Nausea, abdominal pain, tiredness, headache, menstrual changes, dizziness, breast tenderness, and vomiting.

Effectiveness: Used within 72 hours after unprotected intercourse, it will lower the chance of pregnancy by 89 percent. If you are already pregnant, Plan B will not work.

Mis-Conceptions: Debunking Birth Control Myths

Method: Implanon

Already approved by the FDA and ready to launch this month is Implanon, an implanted form of progestin-only birth control.

How It Works: A match-stick sized rod is implanted in a woman's upper arm, where it releases a slow but steady stream of synthetic progesterone for up to three years. This means effortless, round-the-clock protection from pregnancy.

What You Need To Know: If you're thinking this sounds familiar, you're right. A similar device known as Norplant involved six rods implanted in a woman's arm. It met with less than satisfactory results. Problems included scarring on removal. In some instances, major surgery and even plastic surgery became necessary to repair the damage. Ultimately, Norplant was taken off the market.

So how is Implanon different? "First, it's one rod instead of six. And more importantly, doctors are being trained by other doctors on implanting techniques; this should help prevent problems during removal," says Masch.

However, another problem with Norplant was irregular bleeding -- sometimes heavy -- which experts say was related to the form of progesterone used in the device. Implanon uses a different form of progesterone, at a lower dose. Still, some women will experience either more or less bleeding, no bleeding, or breakthrough bleeding.

"If you do, it is likely to continue for the entire three years -- or however long you leave the Implanon in," says Fink.

Moreover, not all doctors are convinced Implanon has moved far enough away from Norplant for them to feel good recommending it.

"I would personally wait quite a long time until there is more experience. Right now it seems Implanon has some of the same issues as Norplant and other forms of progestin-only contraception," says Jon Lischke, MD, a gynecologist with Scripps Memorial Hospital-La Jolla, in San Diego.

Side Effects: Weight gain, headache, mood swings, acne, and depression. Implanon is not recommended if you are pregnant, or think you are pregnant, or have a history of blood blots, unexplained vaginal bleeding, liver disease, or breast cancer.

Effectiveness: Less than one pregnancy per 100 women who use it for one year.

Get the Facts About Emergency Contraception

Method: Continuous-Use Oral Contraceptives

Arguably one of the most exciting advances in contraception was the development of Seasonale -- the first extended-use oral contraceptive that limits menstrual cycles to four per year. Hot on its heels is Lybrel, anticipating FDA approval in early 2007. It will be the first continuous oral contraceptive with no breaks and no periods.

How It Works: Like regular oral contraceptives, both new pills use estrogen and progestin to prevent ovulation. Active pills of Seasonale are used for 84 consecutive days, followed by one week of inactive pills, during which time you experience bleeding. Lybrel is used continuously, with no breaks and no period.

What You Should Know: As radical as this may sound, Steve Goldstein, MD, says if you understand how a menstrual cycle works, it all makes sense.

Normally, he says, a rise in hormones linked to ovulation causes the lining of the uterus to thicken in anticipation of a fertilized egg. If fertilization does not occur, hormone levels drop and the lining is shed in the form of menstrual blood. The pill however, changes all that.

"The pill shuts down your normal hormone production and replaces it with a very tiny amount -- so there is no buildup of the uterine lining," says Goldstein, a professor at NYU Medical Center in New York City. Without a lining, there is no shedding, so the bleeding that occurs when you stop the pill is a "withdrawal bleed caused by a drop in hormones," explains Goldstein.

He believes the monthly bleed you get on the pill is unnecessary. Besides not having to deal with a period, continuous contraception also reduces problems linked to monthly hormone fluctuations, such as PMS, menstrual migraines, mood swings, and increased appetite.

Side Effects: Similar to other forms of oral contraception, there is an increased risk of blood clots and related cardiovascular events, particularly among women who smoke. Additionally, both pills can cause breakthrough bleeding during the first six to 12 months of use. In the case of Seasonale, the total amount of bleeding in the first year is reportedly equal to what you would experience with a monthly period on the 21-day pill cycle. After the first year, breakthrough bleeding usually ceases.

Effectiveness: 99 percent effective against pregnancy when used as directed.

Does ‘Morning After’ Pill Change Sex Habits?

Method: Extended Hormone Oral Contraceptives If you like some of the benefits of a long-term pill, but still want to give your body a break, two relatively new oral contraceptives might be for you: Yaz and Mircette.

How It Works: By providing you with more days on hormones and shorter hormone-free intervals between cycles, these pills are said to reduce menstrual-related symptoms, including the severe form of PMS known as PMDD (premenstrual dysphoric disorder).

"Those extra few days of hormones are believed to keep some of the problems associated with hormone withdrawal under better control," says Fink.

What You Should Know: Yaz utilizes estrogen in combination with a newer form of progestin called drsp (drospirenone), believed to result in milder, more regular periods, and less cramping. Mircette offers 21 days of combined estrogen/progestin therapy, followed by two days of placebo, followed by five days of a lower dose of estrogen alone. It, too, is said to offer women relief from premenstrual woes linked to hormone withdrawal.

Side Effects: Similar to other forms of oral contraceptives, including increased risk of blood clots and stroke, particularly in smokers.

Effectiveness: 99 percent when used correctly and consistently.

Your Complete Guide to Birth Control

Method: Essure One option for birth control has always been tubal ligation, an abdominal surgery that "ties" or otherwise blocks the fallopian tubes so egg and sperm cannot meet. The Essure procedure does the same thing, but without the need for an abdominal incision or general anesthesia.

How It Works: Doctors thread a spiral-like device through the vagina and up into the uterus, and then into each fallopian tube. Once in place, the body's own defenses work to create scar tissue around the device, creating a natural blockage within the tube. No general anesthesia is required and the procedure takes about 35 minutes.

What You Should Know: Backup birth control must be used for three months, after which a special X-ray of the fallopian tubes and uterus checks for adequate blockage. While studies show blockage is substantial at three months and increases at six months, Fink, who was involved in some of the early testing of Essure, said nearly all his patients had to revert to a standard tubal ligation because blockage wasn't sufficient. Erika Banks, MD, a gynecologist at Montefiore Medical Center, believes Essure is a good procedure "if it's done by a doctor who is well trained and is actively doing the procedure," she says.

Banks also cautions women that the process is irreversible and should never be used unless you are 100 percent certain you do not want to become pregnant in the future.

Side Effects: Infection, cramping, bleeding, or dizziness caused by anesthesia.

Effectiveness: 99.8 percent effective in four-year follow-up study.

Note: Use of the contraception options discussed here do not protect against sexually transmitted infections, including HIV.

By Colette Bouchez, reviewed by Louise Chang, MD

SOURCES: Randy A. Fink, MD, gynecologist, Miami. Rachel Masch, MD, MPH, director of family planning and associate director of Reproductive Choice Service, NYU/Bellevue Medical Centers. Jon Lischke, MD, gynecologist, Scripps Memorial Hospital at La Jolla, San Diego. Steve Goldstein, MD, professor of gynecology, NYU Medical Center, New York City. Erika Banks, MD, associate professor of gynecology, Montefiore Medical Center, New York City. Implanon-SA.com. Seasonale.com. Wyeth.com. Yaz-US.com. Micette.com, Essure.com. go2planb.com.