Surgical procedures to place and remove them. The hormone they contain are associated with weight gain.

There are 2 disadvantages that I can think of: The first is that it can cause irregular vaginal bleeding and very irregular periods. The second: It is difficult, sometimes to remove. You can accomplish the same thing with less side effects with the Mirena IUD. Nowadays, the only time I use the implant is with adolescents who I cannot trust to take the birth control pill and who refuse the IUD.
I hope that this helps.

Warmest regards,

Joseph A. Adashek, MD FACOG