The right fit. It's different for every woman who needs birth control.
Three new choices in the United States give women a wider selection and perhaps a better chance at matching a contraceptive to their body and lifestyle, birth control researchers say.
These options, the levonorgestrel intrauterine system, monthly injections and lower-dose pills, use synthetic hormones to prevent pregnancy and are based on previously available methods.
The new birth control options can be especially useful to women who have had negative side effects from another kind of contraceptive or have health risks that can be affected by estrogen, said Kim Custer, spokeswoman for Planned Parenthood in Orange and San Bernardino counties in California.
At the same time, some side effects of the new methods may be beneficial to women, such as decreasing the bleeding in monthly periods or preventing acne.
The newest method is the LNG IUS, or levonorgestrel intrauterine system, which is similar to, but not marketed as, an IUD. It's placed in the uterus and delivers a dose of hormone every day for five years. It's sold under the name Mirena.
The monthly injectable method consists of hormones typically found in birth control pills _ estrogen and progestin _ that a doctor injects into a patient every month. Called Lunelle, this contraceptive joins Depo-Provera, which is administered every three months, as choices for women who prefer injections.
More low-dose birth control pills are emerging, the latest Yasmin, approved in May. These have 20 micrograms of hormones, compared with 30 to 35 micrograms for other pills. They are designed to prevent pregnancy with the lowest possible amount of estrogen and progesterone.
None of these methods protects against sexually transmitted diseases.
Women who are considering birth control for the first time or thinking about switching to a different method should discuss options with their doctor to choose the contraceptive that best fits their health and lifestyle, Custer said.
Here is a primer on these new contraceptives.
Levonorgestrel intrauterine system
This is a T-shaped plastic device that a doctor places in the uterus. It contains a reservoir of levonorgestrel, a hormone used in birth control pills. It is typically inserted within a week of beginning a period to help reduce the risk of being expelled or irregular bleeding. Most women experience no pain during insertion, but one in five feels moderate or severe pain. A woman needs to check the LNG-IUS' strings periodically to ensure that the device is in place. She needs to see the doctor three months after the LNG-IUS is inserted for a followup.
Every 24 hours, the device releases 20 micrograms of levonorgestrel. The hormone makes the mucus thicker at the neck of the cervix, preventing sperm from entering, and thins the lining of the uterus, preventing implantation. It prevents ovulation _ the release of eggs _ in some women.
The LNG-IUS was approved by the Food and Drug Administration in December.
Length of protection: Five years. A doctor removes the device.
Effectiveness: 99.8 percent if used correctly.
Pros: Convenient, easy to use, estrogen-free and makes monthly period lighter and less painful. A woman can conceive within one month of stopping use. Can reduce the number of monthly periods per year.
Cons: Spotting in the first few months, mood changes, acne, headache, breast tenderness and nausea. Cannot be used while breast-feeding. Best for women with one faithful partner; more than one partner can increase risk of pelvic infections.
A doctor or health care professional injects a combination of estrogen and progesterone into the arm, thigh or buttocks. Hormones stop the ovaries from releasing eggs, thicken the cervical mucus to prevent sperm from entering and thin the uterus lining to prevent implantation. Lunelle was approved in October.
Length of protection: 28 to 30 days, no longer than 33 days.
Effectiveness: 99 percent, if used correctly.
Pros: A good choice for women who don't want to have to remember to use a contraceptive every day. Most women who want to conceive start ovulating two to three months after the last injection; some ovulate in the next cycle.
Cons: Not always convenient to get a shot in time each month, may stop the flow of breast milk, may cause weight gain, infection, headache, breast pain and acne.
Cost: About $18 to $25 per shot.
Lower-dose birth control pills
Like traditional birth control pills, these are taken every day or for a cycle of several consecutive weeks. Brands such as Alesse and Loestrin have been introduced in the past five years, and Yasmin was launched this year.
They work by stopping the ovaries from releasing eggs and by thickening the cervical mucus to prevent the entering of sperm.
Length of protection: Continuous.
Effectiveness: 99 percent, if used correctly.
Pros: May help counteract water retention, prevent acne, protect against cancer of the uterus and ovaries, make monthly periods lighter and reduce cramps. Women may conceive one to three months after taking the last pill.
Cons: Yasmin is not recommended for women with kidney, liver or adrenal disease. One of Yasmin's active ingredients _ the hormone drospirenone _ may increase potassium levels that harm the heart.
Side effects of birth control pills include blood clots, stroke and heart attack. Pills should not be taken by women who smoke, especially women older than 35, those who have had a heart attack, stroke, blood clots, certain cancers or liver disease, or unexplained vaginal bleeding and those who are or may be pregnant.
Cost: $10 to $15.