Injectable Progestins Depo-Provera, approved by FDA in 1992, is injected by a health professional into the buttocks or arm muscle every three months. The benefits are similar to those of the minipill and another progestin-only contraceptive, Norplant. Side effects are also similar and can include irregular or missed periods, weight gain, and breast tenderness. Implantable Progestins Norplant, approved by FDA in 1990, and the newer Norplant 2, approved in 1996, are the third type of progestin-only contraceptive. Made up of matchstick-sized rubber rods, this contraceptive is surgically implanted under the skin of the upper arm, where it steadily releases the contraceptive steroid levonorgestrel.
Norplant failures are rare, but are higher with increased body weight.
Some women may experience inflammation or infection at the site of the implant. Other side effects include menstrual cycle changes, weight gain, and breast tenderness. The Paragard IUD can remain in place for 10 years, while the Progestasert IUD must be replaced every year. It's not entirely clear how IUDs prevent pregnancy. They seem to prevent sperm and eggs from meeting by either immobilizing the sperm on their way to the fallopian tubes or changing the uterine lining so the fertilized egg cannot implant in it.