Women's Health

Today's Birth Control Options

The Implant

What it is: The implant is a matchstick-sized rod inserted into the skin of your upper arm by your doctor. Local anesthetic is required; it takes about a minute to put in and two minutes to take out, and works for three years, says Nelson.

How it works: A small amount of progestin is released, suppressing ovulation, thickening the cervical mucus, and thinning the lining of the uterus to help block sperm.

Effective rate: 99%

Drawbacks: The implant can cause irregular bleeding, which is the most common reason women have it removed, says Whitaker. The implant does not protect against STDs.

Benefits: An implant can be used by women who cannot take the female hormone estrogen (such as in birth control pills) and is as effective as sterilization, says Nelson.

Side effects: Some women describe changes in mood or sex drive, and more headaches, acne, and breast tenderness.

The Injectable Hormone

What it is: A doctor gives an injection of progestin every 12 weeks.

How it works: The injection prevents ovulation, thickens cervical mucus to block sperm, and thins the uterine lining, which may prevent an egg from implanting.

Effective rate: 94%

Drawbacks: Some women have irregular bleeding for the first six to 12 months of use. The method does not protect against STDs.

Benefits: About 50% of women stop having periods entirely after one year of use -- a benefit if your periods are heavy, though no one can predict if this will happen to you, Whitaker says.

Side effects: Irregular bleeding and weight gain are the top two side effects, she says. Some women notice headaches, mood changes, and breast tenderness as well as decreased sex drive. Long-term use may weaken bones in women of all ages, and it may not be reversible when you stop using the hormone. Because ovulation can be delayed for some women by nine to 10 months after stopping the hormone injections, "I probably wouldn't recommend this method for women who want to get pregnant within a year," says Nelson.