Implants are small rods that are surgically inserted just under the skin of a woman's upper arm. Each rod slowly releases a progestin hormone into the surrounding tissues where it enters the bloodstream. Progestin is a hormone that prevents pregnancy by preventing ovulation and thickening cervical mucus.

Implanon is a new implant now available in the United States. It consists of a single rod that is implanted under the skin of the upper inner arm and slowly releases low levels of progestin. The rod provides birth control protection for three years but can be removed sooner.

Implanon is as effective as sterilization in preventing pregnancy but it is reversible. It is easy to monitor because the rods can be felt on the inner side of your upper arm. Once positioned under the skin, there is little concern about the device malfunctioning.

Advantages

• The implant is an excellent choice for women who cannot tolerate estrogen, are forgetful about taking their birth-control pills or dislike using diaphragms or hormone injections.
• Implants are also a good choice for women who are breast-feeding because the hormones do not interfere with production or quality of breast milk.
• Implants may reduce the risk of major pelvic infections.
• Fertility resumes immediately after the rod is removed from the arm.

Disadvantages

• Inserting and removing the rod is a surgical procedure performed by a specially trained, experienced health-care provider.
• In some cases, the implant is visible through the skin.
• Irregular bleeding patterns are common during the first year of use.
• Progestin implants should not be used by women with active thrombophlebitis (blood clotting), active liver disease, undiagnosed vaginal bleeding, or a family history of breast cancer.
• Implants do not protect against sexually transmitted diseases.